Note: Descriptions are shown in the official language in which they were submitted.
1 20J6754 20375-682
METHOD AND SYSTEM FOR CONTROLLING RADIO CHANNELS
TO BE USED FOR CORDLESS TELEPHONE SYSTEMS
BACKGROUND OF THE INVENTION
The present invention relates to a method and system for
controlling radio channels to be used for cordless telephone
systems. The present invention is preferably applicable to a
telephone system such as a key telephone system or a home
telephone system including a key service unit and a plurality of
cordless telephone systems.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram showing a prior-art system
configuration of a key telephone system including a plurality of
cordless telephone systems as extension telephone sets;
Figure 2 is a diagram showing a connection operation
sequence executed when an outgoing call is transmitted to an
office line through the cordless telephone system of the prior-
art key telephone system;
Figure 3 is a diagram showing a connection operation
sequence executed when an incoming call is received from an office
line through the cordless telephone system of the prior-art key
telephone system;
Figure 4 is a timing chart showing the operation of the
connecting equipment and the movable telephone set in the
operation sequence shown in Figure 3;
Figure 5 is a block diagram for assistance in explaining
the problem raised when two incoming calls arrive simultaneously
at two cordless telephone systems of the prior-art key telephone
system;
.'~ ~
,~
2 2036754 20375-682
Figure 6 is a block diagram showing the key service unit
of an embodiment of the key telephone system according to the
present invention;
Figure 7 is a block diagram showing the connecting
equipment of the cordless telephone system of the key telephone
system according to the present invention;
Figure 8 is a block diagram showing the movable
telephone set of the key telephone system according to the present
invention;
Figure 9 is a diagram showing a speech channel
designation sequence in the same key telephone system;
Figure 10 is a view showing an example of a table formed
in the RAM 16 shown in Figure 6;
Figure 11 is a view showing a speech channel selecting
sequence in the same key telephone system;
Figure 12 is a diagram showing a connection operation
sequence executed when an outgoing call is transmitted to an
office line through the cordless telephone system of the same key
telephone system;
Figure 13 is a diagram showing a connection operation
sequence executed when an incoming call is received from an office
line through the cordless telephone system of the same key
telephone system; and
Figure 14 is a diagram showing a connection operation
sequence executed when the speech channel designated to the
cordless telephone system at incoming call arrival is unusable.
A prior-art key telephone system including a plurality
of cordless telephone systems as extension telephone sets will be
2a 2 0 3 6 7 5 4 20375-682
described with reference to Figure 1. This telephone system is
composed of a key service unit 3 (referred to as KSU, hereinafter)
connected to office lines 1 and 2 and provided with various
control functions and a plurality of extension telephone sets
connected to the key service unit 3. These extension telephone
sets are wire electric key telephone sets (referred to as EKT,
hereinafter) 8 and 9 and cordless telephone systems 4, 5, 6 and 7.
The cordless telephone system is composed of a movable
telephone set (referred to as TEL, hereinafter) 5 or 7 and a
connecting equipment (referred to as CE, hereinafter) 4 or 6 for
communications between the TEL 5 or 7 and the KSU 3. Here, each
pair of the CE 4 and TEL 5 or the CE 5 and the TEL 7 constitutes
one cordless telephone system, respectively. In each cordless
telephone system, outgoing calls, incoming calls and speech are
enabled to office lines and other telephone sets via the KSU 3, in
the same way as in the ordinary wire EKTs. Further, the KSU 3
including the CEs 4 and 6 is referred to as a base unit herein.
The channels usable for radio communications in the
cordless telephone system are prescribed as shown in Table 1
below:
2036754
TABLE 1
\ CE-Rx CE-Tx
\ (UP-CHANNEL) (DOWN-CHANNEL)
CHANNEL\ TEL-Tx TEL-Rx
NAME
C-CH 254,9625 MHz 381,3125 MHz
S-CH 1254,9500 MHz 381,3000 MHz
S-CH 2254,9375 MHz 381,2875 MHz
.
:
S-CH 41 254,4375 MHz 380,7875 MHz
S-CH 42254,4125 MHz 380,7625 MHz
S-CH 43254,4000 MHz 380,7500 MHz
.
:
S-CH 86253,8625 MHz 380,2125 MHz
In Table 1, the channel C-CH is referred to as a
control channel, which is always used at each
communication start at outgoing and incoming calls. On
the other hand, the channels S-CH 1 to S-CH 86 are
referred to as speech channels, each of which is used
when the control channel is switched to one designated
speech channel after each communication has been started.
Since a multichannel method is adopted with respect to
the speech channels, it is possible to prevent
interference with another cordless telephone system by
designating any one of idling speech channels after the
control channel has been used at each communication
start.
A duplex radio communication is adopted for each
cordless telephone system; that is, two different
frequencies are allocated to the up- and down-channels,
2036754
respectively for communications between the TEL and the
CE. As listed in Table 1, whenever a speech channel
number to be used is determined, the up-channel and down-
channel frequencies can be determined unconditionally.
~~ 5 Further, FM or PM modulation technique~can be applied.
Fig. 2 shows a connection operation sequence
executed when an outgoing call is transmitted through the
prior-art cordless telephone system as shown in Fig. 1,
in which communications between the TEL and the CE via
the control channel are indicated by dashed lines and
those via the speech channel are indicated by solid
lines.
Before an outgoing call, since the cordless
telephone system is in the standby state, the used
lS channel is set to the control channel. In the standby
state, when the TEL is set to an off-hook state, the TEL
transmits an outgoing call signal to the CE via the
control channel as shown in Fig. 2. Since the outgoing
call signal includes an identification code for the TEL,
20 the CE rrc~on~c~ to the outgoing call signal when the TEL
identification code matches an identification code for
the CE itself, designates one speech channel to be used
among a plurality of previously recognized idle speech
channels, and returns the outgoing cal-l signal to the
25 TEL. This outgoing call response signal includes
information indicative of the above-mentioned designated
speech channel. Thereafter, the used channel between the
CE and the TEL is switched from the control channel to
the designated speech channel. After having confirmed
30 the idling state of the designated speech channel again,
the TEL transmits a channel switch-end signal through the
confirmed speech channel. This designated speech channel
is used until the speech ends.
Fig. 3 shows a connection operation sequence
35 executed when an incoming call is received through the
prior-art cordless telephone system as shown in Fig. 1,
2036754
and Fig. 4 is a timing chart showing the operation of the
TEL and the CE.
Before an incoming call, the cordless telephone
system is in the standby state. In the standby state,
5 the TEL turns off a radio transmitting circuit (Tx) and
intermittently turns on or off a radio receiving circuit
(Rx) (e.g. turned off for 2 sec and on for 60 msec), in
order to save a battery. On the other hand, the CE turns
off a Tx and turns on a Rx.
Under these conditions, when an incoming call is
received through the office line, as shown in Figs. 3 and
4, an incoming call command is transmitted from the KSU
to the CE. In response to this command, the CE
designates one channel to be used among a plurality of
15 previously recognized idle speech channels, and turns on
the Tx to transmit an incoming call signal to the TEL
through the control channel. This incoming call signal
includes information indicative of the above-mentioned
designated speech channel. The incoming call signal is
20 repeatedly transmitted for a predetermined limited time
period (e.g. 3.7 sec) until an incoming call response
signal from the TEL is received by the CE.
The TEL maintains the turn-on state when an electric
field is detected under the condition that the Rx is
25 turned on. In response to the incoming call signal, the
TEL turns on the Tx to transmit an incoming call response
signal to the CE through the control channel.
Thereafter, the TEL once turns off the Tx, switches the
channel to be used to the designated speech channel, and
30 turns on the Tx again to transmit a channel switch-end
signal.
In response to the incoming call response signal,
the CE -stops transmitting the incoming call signal, 4~eæ
turns off the Tx, and switches the channel to be used to
35 the designated speech channel. Further, in response to
the channel switch-end signal from the TEL, the CE turns
on the Tx again, and repeatedly transmits an incoming
2036754
call tone (bell) signal to the TEL whenever an incoming
call tone command from the KSU is received. Further, the
TEL generates a calling tone whenever the incoming call
tone signal is received.
In the prior-art cordless telephone system as
described above, however, the control channel is always
used at every communication start. Therefore, there
exists the case where the control channel is occupied by
a single cordless telephone system for several seconds,
in particular at incoming call arrival. Since only one
control channel- is provided, the remaining cordless
telephone systems cannot use the control channel when the
control channel is being occupied by one cordless
telephone system, thus resulting in the following
15 problems:
(l) where an incoming call arrives at a cordless
telephone system, the remaining cordless telephone
systems cannot transmit an outgoing call and receive an
incoming call, for a little while immediately after the
incoming call arrival at one cordless telephone system.
(2) where the TEL 5 of the first cordless telephone
system is placed near the CE 6 of the second telephone
system and additionally the TEL 7 of the second telephone
system is placed near the CE 4 of the first system as
25 shown in Fig. 5 and further two incoming calls arrive at
the two systems simultaneously, since each TEL receives a
strong electromagnetic wave transmitted from each CE
placed in the vicinity of the TEL, an identification
number will not match with each other, so that no call
30 tone is generated.
The similar problem arises between a plurality of
independent cordless telephone systems used within a
relatively small space, as well as between a plurality of
cordless telephone systems used as the extension5 telephone sets in a key telephone system.
SUMMARY OF THE INVENTION
7 2 0 3 6 7 5 4 20375-682
Therefore, the ob~ect of the present lnventlon provldes
a method and an apparatus for controlllng radlo channels to be
used for cordless telephone systems 80 that two or more cordless
telephone systems can slmultaneously transmlt an outgolng call and
recelve an lncomlng call, respectlvely.
Accordlng to a broad aspect of the lnventlon there 18
provlded a method of selectlng and controlllng a channel from a
predetermlned number of channels, to establlsh a speech llnk
between a base unlt and a movable telephone set of a cordless
telephone apparatus, comprlslng the steps of. detectlng ldle
speech channels from a predetermlned number of speech channels ln
the base unlt7 deslgnatlng one speech channel from the detected
ldle speech channels as a speech channel to be used for the
movable telephone set, and storlng lnformatlon lndlcatlve of the
deslgnated speech channel; and controlllng the speech llnk by use
of the deslgnated speech channel to enable speech, when a call 18
orlglnated/recelved by the cordless telephone apparatusl whereln
the steps of detectlng the ldle speech channels, deslgnatlng the
one speech channel and storlng the lnformatlon are performed
before the call 18 orlglnated/recelved by the cordless telephone
apparatus.
Accordlng to another broad aspect of the lnventlon there
18 provlded a method of selectlng and controlllng a channel from a
channel band ln whlch a control channel for transmlttlng control
slgnals to control a speech llnk and a predetermlned number of
speech channels for transmlttlng speech slgnals are arranged
wlthln a predetermlned frequency band, to establlsh a speech llnk
between a base unlt and a movable telephone set of a cordless
203~754
8 _0375-682
telephone apparatus, comprlslng the steps of
detectlng ldle speech channels from a predetermlned number of
speech channels ln the base unlt;
designatlng one speech channel from the detected ldle speech
channels as a speech channel to be used for the movable telephone
set, and storlng lnformatlon lndlcatlve of the deslgnated speech
channel;
transmlttlng the lnformatlon lndlcatlve of the deslgnated
speech channel from the base unlt to the movable telephone set by
use of the control channel, to store the lnformatlon ln the
movable telephone set; and
controlllng the speech llnk by use of the deslgnated speech
channel, wlthout use of the control channel, to enable speech,
when a call ls orlglnated/recelved by the cordless telephone
apparatus;
whereln the steps of detectlng the ldle speech channels,
deslgnatlng the one speech channel, storlng the lnformatlon and
sendlng the lnformatlon are performed before the call ls
orlglnated/recelved by the telephone apparatus.
Accordlng to another broad aspect of the lnventlon there
ls provlded a system havlng a key servlce unlt and at least one
cordless telephone apparatus havlng a base unlt and a movable
telephone set, the apparatus belng connected to the unlt, for
selectlng and controlllng a channel from a predetermlned number of
channels, to e~tabllsh a speech llnk between the base unlt and the
movable telephone set, comprlslng:
detectlng means for detectlng ldle speech channels from a
predetermlned number of speech channels;
~,~
- 9 2036754 20375-682
deslgnatlng means provlded for deslgnatlng one speech channel
from the ldle speech channels detected by sald detectlng means as
a speech channel to be used for the movable telephone set;
communlcatlng means for establlshlng radlo communlcatlon
between the base unlt and the movable telephone set; and
control means for controlllng dlfferent speech channels to be
used by sald base unlt and movable telephone set,
whereln the deslgnated speech channel 18 transmltted from the
base unlt to the movable telephone set before a call 18
0 orlglnated/recelved by the cordless telephone apparatus; and
whereln, when the call 18 orlglnated/recelved by the cordless
telephone apparatus, sald control means control sald communlcatlng
means to use the deslgnated speech channel whlle controlllng the
speech llnk between the base unlt and the movable telephone set.
Accordlng to another broad aspect of the lnventlon there
ls provlded a system havlng a key servlce unlt and at least one
cordless telephone apparatus havlng a base unlt and a movable
telephone set, the apparatus belng connected to the unlt, for
selectlng and controlllng a channel from a channel band ln whlch a
control channel for transmlttlng control slgnals to control a
speech llnk and a predetermlned number of speech channels for
transmlttlng speech slgnals are arranged wlthln a predetermlned
frequency band, to establlsh a speech llnk between the base unlt
and the movable telephone set, comprlslng,
detectlng means for detectlng ldle speech channels from a
predetermlned number of speech channels;
deslgnatlng means for deslgnatlng one speech channel from the
detected ldle speech channels as a speech channel to be used for
- lo ~ 0 3 6 7 5 ~ 20375-682
the movable telephone set;
flrst storing means provlded for the base unlt, for storlng
lnformatlon lndlcatlve of the deslgnated speech channel;
communlcatlng means for establlshlng radlo communlcatlons
between the base unlt and the movable telephone set;
control means for controlllng dlfferent speech channels to be
used by sald base unlt, and movable telephone set; and
second storlng means provlded for the movable telephone set,
for storlng the lnformatlon lndlcatlve of the deslgnated speech
channel;
whereln the lnformatlon lndlcatlve of the deslgnated speech
channel ls transmltted from the base unlt to the movable telephone
set so as to be stored ln sald second storlng means vla the
control channel, before a call ls orlglnated/recelved by the
cordless telephone apparatus; and
whereln, when the call orlglnatedtrecelved by the cordless
telephone apparatus, sald control means control sald communlcatlng
means to use the deslgnated speech channel whlle controlllng the
speech llnk.
Accordlng to another broad aspect of the lnventlon there
ls provlded a key telephone system ln whlch a cordless telephone
system lncludlng a connectlng equlpment and a movable telephone ls
connected to a key servlce unlt as an extenslon telephone set for
mutual radlo communlcatlons, comprlslngz
detectlng means provlded for the connectlng e~ulpment for
detectlng ldle speech channels from a predetermlned number of
speech channels and lndlcatlng the detected ldle speech channels
to the key servlce unlt;
~. .
2036754
11 20375-682
deslgnatlng means provlded for the key servlce unlt, for
deslgnatlng one speech channel from the ldle speech channels
detected by sald detectlng means as a speech channel to be used
for the key telephone system and lndlcatlng the deslgnated speech
channel to the connectlng equlpment~
flrst communlcatlng means provlded for the connectlng
equlpment, for establlshlng radlo communlcatlons between the
connectlng equlpment and the movable telephone set~
flrst control means provlded for the connectlng equlpment,
for controlllng a speech channel to be used by sald flrst
communlcatlng means~
a second communlcatlng means provlded for the movable
telephone set, for establlshlng radlo communlcatlons between the
movable telephone set and the connectlng equlpment~ and
second control means provlded for the movable telephone set,
for controlllng a speech channel to be used by sald second
communlcatlng means5
whereln the deslgnated speech channel lndlcated from the key
servlce unlt to the connectlng equlpment 18 lndlcated from the
connectlng equlpment to the movable telephone set vla radlo
communlcatlons between sald flrst and second communlcatlng means,
before a call 18 orlglnated/recelved by the cordless telephone
system; and
whereln, when the call 18 orlglnated/recelved by the cordless
telephone system, sald flrst and second control means controls
sald flrst and second communlcatlng means to use the deslgnated
speech channel whlle controlllng a speech llnk between the
connectlng equlpment and the movable telephone set.
12 2036754 20375-682
DB~ ON OF TH13 ~n~r dRR~3D E ~D3ODIMI~NTS
An embodlment of the present lnventlon wlll be descrlbed
herelnbelow wlth reference to the attached drawlngs.
Flgure 6, Flgure 7 and Flgure 8 show a key servlce unlt
(KSU), a connectlng equlpment (CE) and a movable telephone set
(TEL) accordlng to the present lnventlon, respectlvely whlch are
all lncorporated ln a key telephone system as shown ln Flgure 1.
2036754
As shown in Fig. 6, the KSU 100 includes office line
interface circuits 10 and 11, electric key telephone set
(EKT) interface circuits 13 and 14, a switching circuit
12, a controller 15, a power supply circuit 24, etc.
Each office line interface circuit 10 or 11 is
connected to each office line 1 or 2 and provided with
various functions of detecting an incoming call signal
transmitted through each office line and outputting it to
the controller 15, acquiring each office line in
accordance with a control data outputted from the
controller 15, transmitting a select signal to the
acquired office line in accordance with the control data
from the controller 15, transmitting speech signals
between the acquired office line and the switching
circuit 12, etc.
Each EKT interface circuit 13 or 14 is connected to
an extension telephone set such as a wire electric key
telephone set (EKT), a cordless telephone system via
speech signal lines 18 and 20 and control lines 19 and
21, and provided with various functions of supplying
power to each extension telephone set, transmitting
speech signals between each extension telephone set and
the switching circuit 12, transmitting control data
between each extension telephone set and the controller
via a data interface circuit 17 including buffer
memory and parallel/serial converting circuits.
The switching circuit 12 is connected to office line
interface circuits 10 and 11 and the EKT interface
circuits 13 and 14, and provided with a function of
switching connections between an office line and an
extension telephone set in accordance with control data
from the controller 15. This switching circuit 12 is
connected to an oscillator 22 for generating an extension
dial tone (400 Hz). That is, in response to an outgoing
call signal from an extension telephone set, this
switching circuit 12 connects the oscillator 22 to an EKT
interface circuit generating an outgoing call signal to
,~ ,.
,, 1~
;~ 2036754
transmit an extension dial tone to a telephone set to
which the outgoing call signal is transmitted. However,
any switching circuits can be applied to the key service
unit.
The controller 15 is a microcomputer including a CPU
15a, a ROM 15b for storing control programs, a RAM 15c,
etc. to control various system operations such as
outgoing call, incoming call, connection, speech, speech
end, etc. in accordance with the stored programs. In
control operation, necessary control data are
received/transmitted between the controller 15 and the
various circuits such as the office line interface
circuits 10 and 11, the EKT interface circuits 13 and 14,
the speech switching circuit 12, etc.
The control programs include a program for
designating a speech channel through which each cordless
telephone system is used, and transmitting the designated
speech channel to each cordless telephone system
connected to the KSU 100. This program is executed by
the CPU 15 as a part of the initial routines executed
whenever the movable telephone set is turned on. The
functions executed by the microcomputer in accordance-
with this program are shown as a block diagram within the
CPU 15a. Further, a RAM 16 iS connected to the
25 controller 15. This RAM 16 includes a table which
records speech channels to be used by each cordless
telephone system designated in accordance with the
e~se~t ~ nvention, as shown in Fig. 10. The RAM 16 is
~ by a lithium battery 25, so that the table is
30 kept recorded even at power failure.
The power circuit 24 converts a commercial 100 V AC
supply voltage into a predetermined stabilized DC supply
voltage and supplies it to the KSU 100. The converted
supply voltage is also supplied to each extension
35 terminal set via each EKT interface circuit 13 or 14.
~ 2036754
With reference to Fig. 7, the connecting equipment
(CE) of the cordless telephone system will be described
hereinbelow.
The CE 200 is connected to the EKT interface circuit
(e.g. 13) shown in Fig. 1 via a speech signal line (e.g.
18) and a control signal line 19, and provided with a
hybrid circuit 30, a speech receiving circuit 31, a
speech transmitting circuit 32, a radio transmitting
circuit (Tx) 34, a radio receiving circuit (Rx) 38, a
10 controller 36, a power circuit 41, etc.
The hybrid circuit 30 converts two lines to 4 lines
or vice versa between the speech signal line 18 connected
to the KSU 100 and the speech signal lines connected to
the speech receiving circuit 31 and the speech
- 15 tra~smitting circuit 32. This hybrid circuit 30 includes
ng ~network 33 to control a sidetone to an
appropriate level by simulating the line impedance.
The speech receiving circuit 31 receives speech
signals outputted from the hybrid circuit 30 and
20 transmits them to the Tx 34. ~ local oscillator signal
~ /oC~c~
is given from a PLL'~'circuit 35 to the Tx circuit 34. The
carrier frequency of the local oscillator signal is
controlled by the controller 36 so as to match one of
down-channel frequencies (shown in Table 1) designated by
25 the KSU 100 as a speech channel for the cordless
telephone system. However, in a specific case, the
~ carrier frequency of the Tx 34 is controlled so as to
match that of the down-channel of the control channel, as
described later. The output signal of the Tx circuit 34
30 is transmitted to an antenna 45 via an antenna sharing
(duplex) device (DUP) 37 and then radio-transmitted to
the TEL 300.
The signals transmitted from the TEL 300 are
received via the antenna 45 and then inpu~ed to the Rx
35 38 via the antenna sharing device 37. ~ Rx 38 is
composed of a control channel (C-CH) receive section 38a
and a speech channel (S-CH) receive section 38b. The
I~o
. 203~5
C-CH receive section 38a is fixedly tuned to the up-
channel frequency (shown in Table 1) of the control
channel. On the other hand the S-CH receive section 38b
receives a local oscillator signal from the PLL circuit
5 39. The frequency of the PLL circuit 52 is controlled by
the controller 36 so that the S-CH receive section 38b is
tuned to one of up-channel frequencies (shown in Table 1)
designated by the KSU 100 as a speech channel to be used
as the cordless telephone system. The speech
10 transmitting circuit 32 receives speech signals
transmitted from the TEL 300 and received by the Rx 38
and control data, and transmits the speech signals to the
hybrid circuit 30 and the control data to the controller
36.
The data line 19 from the KSU 100 is connected to a
power circuit 41 and a data interface circuit 42 via a
transformer 40. The power circuit 41 converts a power
from the KSU 100 into a predetermined DC voltage level
and then supplies it to the CE 200. The data interface
20 circuit 42 includes serial/parallel converters and buffer
memory units to receive/transmit control data between the
data line 19 and the controller 36.
- The ~ ntroller 36 is a microcomputer including a CPU
36a, a 36b for storing control programs, a RAM 36c,
25 etc. to control operations of the speech receiving
circuit 31, speech transmitting circuit 32, Tx 34, PLL
circuits 35 and 39, etc. in accordance with stored
programs. One of the control operations executed by this
microcomputer is to control the afore-mentioned
30 frequencies of the Rx 31 and the Tx 34 in order to
determine the radio channel used by this CE 200. The
functions executed by the microcomputer in accordance
with the program are shown as a block diagram within the
CPU 36a. This controller 36 includes a radio data
35 interface circuit 36d having a modem. Therefore, the
interface circuit 36d receives the speech frequency
signal from the movable telephone set via the speech
~,
- ~ 2036754 20375-682
transmitting circuit 32, demodulates the speech signal into
control data and gives them to the CPU 36a. Further, the
interface circuit 36d modulates control data to be transmitted
from the CPU 36a to the movable telephone set into speech
frequency signals and gives them to the speech receiving circuit
31. Further, the controller 36 receives/transmits control data
from/to the KSU 100 via a data interface circuit 42.
An EEPROM (electrically erasable programmable read only
memory) 43 and a speech channel clear switch 44 are connected to
the controller 36. In this EEPROM 43, identification numbers of
the cordless telephone systems and a speech channel number
designated by the KSU 100 as a cordless telephone system to be
used are recorded. With reference to the EEPROM, the CPU 36
controls the frequency of the PLL circuits 35 and 39. When turned
on, the speech channel clear switch 44 erases the speech channel
recorded in the EEPROM 43 as a channel to be used, so that the CE
200 is returned to an initial condition where a channel to be used
is not yet designated. This switch 44 is used to designate the
speech channel to be used again when the electric wave condition
is poor at the designated speech channel. The same clear switch
is also provided for the TEL 300. In case of poor electric wave
condition, it is necessary to depress the clear switch of the
telephone set, simultaneously.
With reference to Figure 8, the movable telephone set
(TEL) 300 will be described hereinbelow.
The TEL 300 includes an antenna 30, a radio receiving
circuit (Rx) 51, a speech receiving circuit 53, an earphone 54, a
microphone 55, a speech transmitting circuit 56, a radio
~ 2036754 20375-682
transmitting circuit (Tx) 57, a controller 59, a sounder 63, a
power circuit 66, dial and function keys 68.
Electric wave transmitted from the CE 200 is received by
the antenna and inputted to the Rx via an antenna sharing (duplex)
device (DUP) 50. The Rx 51 is
2036754
composed of a control channel (C-CH) receive section 51a
and a speech channel (S-CH) receive section 51b. The
C-CH receive section 38a is fixedly tuned to the down-
channel frequency (shown in Table 1) of the control
5 channel. On the other hand, the S-CH receive section 51b
receives a local oscillator signal from the PLL circuit
52. The frequency of the PLL circuit 52 is controlled by
the controller 59 so that the S-CH receive section 51b is
tuned to one of down-channel frequencies (shown in Table
10 1) designated by the KSU 100 as a speech channel to be
used as the cordless telephone system. The speech
signals transmitted by the CE 20 and received by the Rx
51 and control data are given to the speech receiving
circuit 53. The speech signals are transmitted to the
15 earphone 54 and the control data are transmitted to the
controller 59. The speech signals from the microphone 55
are inputted to the speech receiv ~g circuit 56 and then
transmitted to the Tx 57. The 57 ~eceives a local
oscillator signal from the PLL circuit ~. The frequency
20 of the PLL circuit ~ is controlled by the controller 59
so that the carrier frequency of the Tx 57 matches one of
up-channel frequencies (shown in Table 1) designated by
the KSU 100 as a speech channel for the cordless
telephone system. However, in a specific case, the PLL
25 circuit 58 is controlled so that the carrier frequency of
the Tx 57 matches the up-channel frequency of the control
channel, as described later. The output signal of the Tx
57 is transmitted to an antenna 73 via an antenna sharing
(duplex) device (DUP) 50, and then transmitted to the CE
30 200.
The controller 59 is a microcomputer including CPU
59a, a ROM 59b for storing control programs, a RAM 59c,
etc. to control operations of the speech receiving
circuit 51, a radio receiving circuit 51, a speech
35 receiving circuit 53, a speech transmitting circuit 56, a
radio transmitting circuit 57, PLL circuits 52 and 58,
etc. in accordance with stored programs. One of the
.,
.
~b
~ 2036754
control operations executed by this microcomputer is to
control the afore-mentioned frequencies of the Rx 51 and
the Rx 57 in order to determine the radio channel used by
this TEL 300. The functions executed by the
5 microcomputer in accordance with the program are shown as
a block diagram within the CPU 59a. This controller 59
includes a radio data interface circuit 59d having a
modem. Therefore, the interface circuit 59d receives the
speech frequency signal (control data) from the CE 200
10 via the speech receiving circuit 53, demodulates, and
transmits the speech signal to the CPU 59a. Further, the
interface circuit 59d modulates control data to be
transmitted from CPU 59a to the CE 200 into speech
frequency signals and gives them to the speech receiving
15 circuit 56.
An EEPROM 60 and a speech channel clear switch 61
are connected to the controller 59. In the same way as
in the connecting equipment 200, identification numbers
of the movable key telephone sets and a speech channel
20 designated by the KSU 100 as a cordless key telephone
system to be used are recorded in this EEPROM 60.
Further, when turned on, the speech channel clear switch
61 returns the movable key telephone set to an initial
condition where a channel to be used is not yet
25 designated.
In addition, a sounder 63, dial and function keys
68, a hook key 69, a speech lamp 70, an unusable lamp 70
are connected to the controller 59. A call tone signal
(when an incoming call arrives) or a confirmation tone
30 signal (when the dial and function keys 68 are depressed)
are given from the controller 59 to the sounder 63 via an
amplifier 62. The dial and function keys 68 are
depressed when a dialing or a function selection is
required. The hook-key 69 is a switch turned on when
35 once depressed and off when depressed again. Therefore,
controller 59 recognizes an on-hook state of the movable
telephone set when the hook key 69 is turned on and an
2036754
off-hook state thereof when turned off. The controller
59 turns on the speech lamp 70 during speech and turns on
the unusable lamp 71 when the movable telephone set is
carried out of an area within which electric wave
transmitted from the CE can reach.
The power circuit 66 regulates the output voltage of
a nickel-cadmium battery 65 to a predetermined voltage
level and supplies the regulated voltage to the movable
telephone set (TEL) 300. Further, since the power
circuit 66 is provided with a charge terminal 67, the
battery 65 can be charged by connecting an external
charger (not shown) to this terminal. The power switch
64 is used to turn off the power circuit 66 to prevent
battery consumption when the movable key telephone sets
300 are all not used.
The operation of the key telephone system will be
described hereinbelow.
After the system has been installed and the
necessary wiring work has been completed by a worker, the
20 KSU 100 is turned on. Then, an initial routine is
executed to initialize all the data (e.g. extension
numbers of the telephone sets, various functions, etc.)
required to operate the system. In this initial routine,
a procedure of designating a speech channel to each
25 cordless key telephone system is of course included in
the initial routine. Fig. 9 shows an operation sequence
of the speech channel designation. The speech channel
designating operation will be explained in further detail
with reference to Figs. 6, 7, 8 and 9.
When the KSU 100 is turned on, a reset section 15g
commands a table write section 15h to clear all the
information recorded in a table (as shown in Fig. 10) in
the RAM 16. This table clear signal is given- to a flag
section 15i. This flag section 15i sets or resets a flag
indicative of whether a speech channel to be used has
already been designated or not for each cordless
telephone system. In response to the table clear signal,
. .,_
2036754
the flag section 15i sets a flag indicative of that all
the speech channels for all the cordless telephone
systems are not yet designated.
Further, when the KSU 100 is turned on, power is
5 supplied to the CE 200. Therefore, in the CE 200 as
shown in Fig. 7, a reset section 36n of the controller 36
commands a ROM write section 36j to clear all the channel
numbers previously stored in the EEPROM 43. The fact
that the speech channel numbers are all cleared in the
10 EEPROM 43 is detected by a flag section 36g, so that the
flag section 36g sets a flag indicative of that the
speech channels are not yet designated. Further, a radio
control section 36h turns on the radio receiving circuit
38 and the speech transmitting circuit 32. Further, in
15 response to a command from the reset section 36n, a
channel scan section 36i scans the local oscillation
frequencies all over the frequency range to search the
idle/busy states of all the local speech channels at the
spot where the connecting equipment is installed, on the
20 basis of a noise detection signal (ND) outputted from the
speech transmitting circuit 32 at each frequency. The
channel scan section 36i transmits idle/busy speech
channel numbers (as shown in Table 1) obtained as a
result of the scanning operation to a data transmit
25 section 36~. The data transmit section 36~ transmits the
data to the KSU 100 via the control signal line 19. The
above-mentioned data are referred to as local idle speech
channel data, hereinafter. In the KSU 100 shown in Fig.
~, a table write section 15h of the controller 15
30 receives the local idle speech channel data from all the
CEs via a data receive section 15e, sums up these data,
and records the data into a table within the RAM 16.
Thereafter, when a clear key 61 of the TEL 300 as
shown in Fig. 8 is depressed, a reset section 59j
35 commands a ROM write section 59h to clear all the speech
channel numbers previously stored in the EEPROM 60. The
fact that the speech channel numbers are all cleared in
~3
20367~4
the EEPROM 60 is detected by a flag section 59i, so that
the flag section 59i sets a flag indicative of that the
speech channels are not yet designated. Thereafter, the
hook key 69 is depressed by a worker. Then, a hook-state
5 detect section 59g of the controller 59 recognizes an
off-hook and indicates it to a radio data transmit
section 59f and a radio control section 59g. Then, the
radio control section 59g turns on the speech
transmitting circuit 56 and the radio transmitting
10 circuit 57, and the radio data transmit section 59f
transmits an outgoing call signal to the speech receiving
circuit 56 via the radio data interface circuit 59d. In
this transmission, the radio control section 59g
determines a radio speech channel to be used in
15 accordance with the channel numbers stored in the EEPROM
60. In this case, when the channel numbers stored in the
EEPROM 60 have been already cleared as described before,
the radio control section 59g controls the PLL circuit 58
so that the control channel can be used. Since the
20 channel numbers have been already cleared in the EEPROM
43 in the CE 200, the radio control section 36h controls
the PLL circuit 39 so that the control channel can be
used. Accordingly, the outgoing call signal is
transmitted from the TEL 300 to the CE 200.
The outgoing call signal received by the CE 200 as
shown in Fig. 7 is transmitted from the speech
transmitting circuit 32 to the radio data interface
circuit 36d to compare the identification number of the
TEL 300 included in the outgoing call signal with the
30 identification number read from the EEPROM 43. When both
the identification numbers match each other, this
outgoing call signal is transmitted to a radio data
receive section 36e of the CPU 36a. In response to the
outgoing call signal, the radio data receive section 36e
35 refers to the flag section 36g. As already described,
the flag section 36g indicates the state where the speech
channel is not yet designated. Therefore, the radio data
2036754
receive section 36e transmits a speech channel
designation request signal to the data transmit section
36e. The data transmit section 36e transmits the request
signal to the KSU 100 via the control signal line 19.
In the KSU 100 shown in Fig. 6, the above channel
designation request is transmitted to a data receive
section 15e via the EKT interface circuit 13, and then
given to a channel select section 15j. The channel
select section 15j selects an idle speech channel from
10 among local idle speech channel data recorded in the RAM
16, and gives the selected idle speech channel number to
a data transmit section 15d and a table write section
15h. The data transmit section 15d returns the channel
number data to the CE 200 via the EKT interface circuit
15 13 as a designated speech channel data.
In the CE 200 shown in Fig. 7, a data receive
section 36m receives this designated speech channel data,
and gives it to a radio data transmit section 36f, a
radio control section 36h and a ROM write section 36i.
20 The radio data transmit section 36f forms an outgoing
signal response signal and transmits it to the TEL 300.
This outgoing call response signal includes the above-
mentioned designated speech channel number data. This
outgoing call response signal is transmitted via the
25 control channel. Therefore, the radio control section
36h controls the PLL circuits 35 and 39 so that the
control channel is switched to the designated speech
channel as a channel to be used.
In the TEL 300 shown in Fig. 8, in response to the
30 outgoing call response signal, a radio data receive
section 59e refers to the flag section 59i. Since the
speech channel is not yet designated, the designated
speech channel number data is extracted from the outgoing
call response signal, and then given to the radio control
35 section 59g and to ROM write section 59h. Then, the
radio control section 59g controls the PLL circuits 35
-~ and 39 so that the channel to be used is switched from
2036754
the control channel to the designated speech channel and
subsequently the designated speech channel is checked as
to whether the designated speech channel is idle on the
basis of a carrier detection signal (CD) from the speech
receiving circuit 53. If idle, the radio control section
59g gives its idle state to the radio data transmit
section S9f. The radio data transmit section 59f forms a
channel switch end signal and transmits its signal to the
CE 200 via the designated speech channel. Thereafter,
the ROM write section 59h writes the designated speech
channel number data in the EEPROM 60, and commands the
i~dlca~Jn 7
flag section 59i to set the flag indicaLi~ of that the
channel has been designated. 3~ e
In the CE 200, the radio data receive section ~ge
receives the channel switch end signal from the TEL, and
gives its signal to the data transmit section 36c, the
radio data transmit section 36f and the ROM write section
36i. Therefore, the data transmit section 36e transmits
an off-hook signal to the KSU 100, and the radio data
transmit section 36f transmits a speech circuit turn-on
signal to the TEL 300. Further, the ROM write section
36i writes the designated speech channel number data in
the EEPROM 43, and gives its write end to the flag
section 36g to set a flag indicative ~ that the speech
25 channel has been designated.
In the KSU 100 shown in Fig. 6, when the data
receive section 15e receives the off-hook signal, the
data receive section 15e knows that the speech channel is
not yet designated with reference to the flag section 15i
30 and commands the table write section 15h to write the
designated speech channel number data in a table within
the RAM 16. Further, since the off-hook signal is given
to a call control section 15f, the call control section
15f controls a switching circuit 12 so that an oscillator
22 is connected to the EKT interface circuit 13 to
transmit an extension dial tone from the oscillator 22 to
the CE 200 via the speech signal line 18. The CE 200
< ~
~ 20367S4
transmits the extension dial tone received through the
speech signal line 18 to the TEL 300. In the TEL 300
shown in Fig. 8, the radio control section 59g receives
the speech circuit turn-on signal via the radio data
receive section 59e to turn on the speech circuit
provided in the speech receiving circuit 53 and the
speech transmitting circuit 56, respectively to connect
the earphone 54 and the microphone 55 to the radio
receiving circuit 51 and the radio transmitting circuit
57, respectively. Accordingly, the received extension
dial tone is transmitted to the earphone 54. When
hearing the extension dial tone, the worker knows that a
speech channel to be used for this TEL has been
designated and registered.
Thereafter, when the worker turns off the hook-key
69 of the TEL 300 again, a hook-state detect section 59k
recognizes an on-hook state and transmits a speech end
signal to the CE 200 via the radio data transmit section
59f. The CE shown in Fig. 7 receives the on-hook signal
20 and transmits it to the KSU 100, so that the KSU 100
recognizes that the channel designation procedure for the
movable telephone set has been completed.
After the above-mentioned channel designation has
been completed to one cordless telephone system, another
25 cordless telephone system is off-hooked and another
speech channel is designated to the cordless telephone
system in accordance with the same sequence as described
above. That is, the similar sequence is repeated for all
the cordless telephone systems.
Fig. 10 shows an example of a table formed in the
RAM 16 of the KSU 100 after the speech channels have been
designated to all the cordless telephone systems. This
table includes a map indicative of designated speech
channels for cordless telephone systems (a designated
35 speech channel map) and a map indicative of idle speech
channels at cordless telephone system locations (a local
idle speech channel map). In this example, four TELS
a~
~f~
2036754
having identification numbers 1 to 4 are listed, in which
indicates a cordless telephone syst~em and "0"
indicates an electric key telephone set }~ the kind of
telephone sets. In the designated speech channel map,
"1" indicates a designated speech channel. In the local
idle speech channel map, "0" indicates an idle speech
channel. It is preferable to rewrite the local idle
speech channel map occasionally so as to follow change in
environment. For the purpose, in the CE 200 shown in
Fig. 7, a channel scan section 36i scans the speech
channels periodically in response to a synchronizing
signal outputted from a timer 36k to transmit information
as to local idle speech channels to the KSU 100. In the
KSU 100 shown in Fig. 6, a table rewrite section 15h
rewrites the local idle speech channel map within the RAM
16 on the basis of the local idle speech channel
information periodically transmitted from the CE 200.
By the way, when each speech channel is designated
to each cordless telephone system in sequence, it is
necessary to prevent a speech channel from being
designated to two or more cordless telephone systems.
For the purpose, the KSU 100 designates the speech
channels in accordance with a selected sequence as shown
in Fig. 11, for instance. In more detail, the speech
channel No. 1 (S-CH 1) is designated to the first
cordless telephone system; the speech channel No. 6 (S-CH
6) is designated to the second cordless telephone system;
the speech channel No. 11 (S-CH 11) is designated to the
third cordless telephone system; and so on. That is, the
speech channel is designated at intervals of five speech
channel numbers. After the last speech channel No. 86
has been designated, the speech channel No. 2 is
designated, and then other speech channels are designated
at intervals of five speech channel numbers. In this
designation, the speech channels now being used
(indicated by "1" in the local idle speech channel map
shown in Fig. 10) are passed without being designated.
-
r
2036754
Further, the relationship between the speech channelnumbers and the frequencies are listed in Table 1. The
reason why the speech channels are designated to the
cordless telephone systems at intervals of five channel
numbers without being designated in the order of No. 1,
No. 2, ... in sequence is to sufficiently increase
difference in frequency of the channel to be used between
the cordless telephone systems for prevention of radio
interference with each other. However, it is also
possible to adopt other methods of preventing the speech
channels from being designated doubly.
The operation will be described, which is executed
when an outgoing call is transmitted from the cordless
telephone system to the office line or an incoming call
is transmitted from the office line to the cordless
telephone system after the initial routine has been
completed.
Fig. 12 shows the connecting operation sequence
executed when an outgoing call is transmitted from the
cordless telephone system to the office line. The
outgoing call operation will be explained with reference
to Figs. 6 to 12. When the TEL 300 is off-hooked, an
outgoing call signal is transmitted from the TEL 300 to
the CE 200. In the TEL 300 and the CE 200, the radio
control sections 59g and 36h have already set the used
speech channel to the designated speech channel in
accordance with the channel number stored in the EEPROMs
and 43, respectively. Therefore, all the radio
communications including the outgoing call signal
transmission are always effected through the designated
speech channel, without using the control channel.
Further, when transmitting the outgoing call signal, the
radio control section 59g of the TEL 300 first confirms
whether the designated speech channel can be used; that
is, the frequency of the designated speech channel is not
used for the other adjacent cordless telephone systems,
on the basis of the carrier detection signal CD. When
-
q- -
2036754
the idling state of the designated speech channel has
been confirmed, this information is given to the radio
data transmit section 59f to transmit the outgoing call
signal.
In the CE 200 shown in Fig. 7, the radio data
interface circuit 36d receives the outgoing call signal
and checks whether the identification number of the TEL
300 included in the outgoing call signal matches its
identification number stored in the EEPROM. If matches,
the received outgoing call signal is transmitted to the
radio data receive section 36e. The radio data receive
section 36e transmits an off-hook signal to the KSU 100
via the data transmit section 36~ and further transmits
an outgoing call response signal to the TEL 300 via the
radio data transmit section 36f. In the TEL 300 shown in
Fig. 8, in response to the outgoing call response signal,
the radio control section 59g turns on the speech circuit
on the basis of the command from the radio data receive
section 59e. Further, in the KSU 100 shown in Fig. 6, in
response to the off-hook signal, the call control section
15f controls the switch circuit 12 to transmit an
extension dial tone to the CE 200. The CE 200 further
transmits this dial tone to the TEL 300.
In the TEL 300 shown in Fig. 8, when the user hears
the extension dial tone from the earphone 54, the user
enters a predetermined number (e.g. "0") for calling an
office line through the dial keys 68. Then, the dial
signal of "0" is transmitted to the CE 200, and therefore
the CE 200 transmits the corresponding dial data "0" to
the KSU 100. In the KSU 100 shown in Fig. 6, the data
receive section 15e receives this dial data "0" and gives
it to the call control section 15f. The call control
section 15f controls the office line interface circuit 10
to acquire an idle office line (e.g. 1) (to close a dc
loop) and further controls the switching circuit 12 to
connect the office line interface circuit 10 of the
acquired office line to the EKT interface circuit 13 of
3 ;~
~''.~
2036 754
the cordless telephone system which transmits an outgoing
call signal.
When detecting the above acquisition, the telephone
office transmits a dial tone (office line dial tone) to
an office line 1, so that this dial tone is transmitted
from the KSU 100 to the TEL 300 via the CE 200. When
hearing this office line dial tone, the user enters a
telephone number of a called subscriber through the dial
keys 68. Therefore, the TEL 300 transmits the dial
signals indicative of the called subscriber's number to
the CE 200. The CE 200 transmits a dial data
corresponding thereto to the KSU 100. The KSU 100
transmits the corresponding selection signal to the
office line in the form of dial pulses or MF signals.
At the speech end, since the TEL 300 is on-hooked, a
speech end signal is transmitted to the CE 200. In
response to the speech end signal, the CE 200 transmits
the on-hook signal to the KSU 100. In response to the
on-hook signal, the KSU 100 opens the DC loop of the
office line, so that the speech ends.
With reference to Figs. 6 to 8 and 13, the
connecting operation sequence executed when an incoming
call is transmitted to the cordless telephone system will
be explained hereinbelow.
The call signal of 16 Hz, for instance is repeatedly
transmitted intermittently from the telephone office to
the KSU 100. In the KSU 100 shown in Fig. 6, in response
to the first call signal, the call control section 15f
transmits an incoming call command to the CE 200. Since
the cordless telephone system is in the standby state
before the incoming call arrival, in this state the radio
receiving circuit 38 is turned on and the radio
transmitting circuit 34 is turned off in the CE 200. In
response to an incoming call command in this state, the
radio control section 36h of the CE 200 turns on the
radio transmitting circuit 34, and further the radio data
transmit section 36f transmits an incoming call signal to
31
2036754
the TEL 300. As already described, since the radio
control section 36h allows the radio receiving circuit
(Rx) 38 and the radio transmitting circuit (Tx) 34 to be
set to the speech channel designated in accordance with
the channel number stored in the EEPROM, all the radio
communications including the incoming call signal
transmission are always effected through the designated
speech channel without using the control channel.
Further, when transmitting the incoming call signal, the
radio control section 36h of the CE 200 first confirms
whether the designated speech channel can be used; that
is, the frequency of the designated speech channel is not
used for the other cordless telephone systems, on the
basis of the noise detection signal. When the idling
state of the designated speech channel has been
confirmed, the information is transmitted.
In the TEL 300, the radio control section 59g turns
off the radio transmitting circuit 57 and intermittently
turns on the radio receiving circuit 53 (e.g. turned off
for 2 sec and on for 60 msec) in the standby state.
While the radio transmitting circuit 53 is turned on, if
a carrier is detected, the radio control section 59 keeps
the radio receiving circuit 53 in the turn-on state. In
this state, when receiving the incoming call signal, the
TEL 300 returns an incoming call response signal to the
CE 200.
Thereafter, whenever a call signal arrives, the KSU
100 transmits an incoming tone command to the CE 200. In
the CE 200, when the radio data receive section 36e
receives the incoming call response signal from the TEL
300, this information is given to the radio data transmit
section 36f to transmit an incoming call tone signal to
the TEL 300. In the TEL 300, the sounder 63 is activated
in response to the incoming call tone signal to generate
a call tone (bell sound). The CE 200 keeps transmitting
the incoming call tone command to the TEL 300 until the
TEL 300 is off-hooked.
~ .
33
.
203675
When the TEL 300 is off-hooked, an off-hook data is
transmitted to the CE 200. In response to the off-hook
data, the CE 200 transmits the off-hook signal to the KSU
100. In response to the off-hook signal, the call
S control section 15f of the KSU 100 controls the office
line interface circuit 10 to acquire the office line 1
and further controls the switching circuit 12 to connect
the office line 1 to the cordless telephone system, so
that speech begins.
The operation sequence of speech end is the same as
that of the outgoing call.
As described above, in the method of the present
invention, since radio communications can be always
effected by use of each speech channel so designated as
not to be overlapped with each other or not to be used
doubly, it is possible to simultaneously process outgoing
calls or incoming calls for a plurality of cordless
telephone systems. In addition, since it is unnecessary
to switch the channel to be used from the control channel
to the speech channel at the start of the radio
communications, being different from the prior-art
method, it is possible to shorten the time interval from
the start of an outgoing or incoming call to the end of
the connection between the office line and the TEL.
By the way, there exist some cases where a speech
channel once designated cannot be used because the same
speech channel is being used for the other adjacent
cordless telephone systems. In this case, an outgoing
call is inhibited in the above embodiment. Further, an
incoming call is transmitted to the TEL 300 by
temporarily using the control channel.
Fig. 14 shows the operation sequence of the incoming
call under these unusable conditions. In response to the
incoming call command from the KSU 100, the CE 200 checks
whether the designated speech channel is now idle or not.
If not idle or busy, the CE 200 requests the KSU 100 to
designate a new idle speech channel. The KSU 100 refers
-
~ . 3~
~.
2036754
to the local idle channel map to designate another idle
speech channel and indicates it to the CE 200. The CE
200 switches the channel of the Tx 34 to the control
channel, and transmits the incoming call signal to the
TEL 300 through the control channel. A data indicative
of the newly designated idle speech channel is included
in this incoming call signal. Therefore, the TEL 300
receives the incoming call signal of the C-CH receive
section 51a of the Rx 51, and transmits it to the radio
data receive section 59e. The radio data receive section
59e commands the radio control section 59g to switch the
channel of the Tx 57 to the control channel. Therefore,
the incoming call response signal is transmitted from the
TEL 300 to the CE 200 through the control channel, and
received by the C-CH receive section 38a of the Rx 38 in
the CE 200. Thereafter, in both the CE 200 and TEL 300,
the channel to be used is switched from the control
channel to the newly designated speech channel. The TEL
300 checks whether the newly designated speech channel is
idle or not. If idle, a channel switch end signal is
transmitted from the TEL 300 to the CE 200 and further
from CE 200 to the KSU 100. Then, the newly designated
speech channel is stored in the KSU 100, the CE 200 and
_ the TEL 300, so as to be used principally. ~ operation
sequence after that is the same as that described with
reference to Fig. 13.
As described above, when another channel is required
to be designated because the designated channel is used
doubly by another cordless telephone system, the user
depresses the speech channel clear keys 44 and 61 of the
TEL 300 and the CE 200. Then, in the TEL 300 and the CE
200, the reset sections 59j and 36n command the ROM write
sections 59h and 36j to return the contents stored in the
EEPROMS 60 and 43 to those stored before designated.
Further, the CE 200 indicates this reset operation to the
KSU 100. Then, in the KSU 100, the reset section 15g is
activated to execute again the afore-mentioned operation
.
3~
2036754
sequence of designating a speech channel for the reset
cordless telephone system. Therefore, the channel to be
used for the cordless telephone system is designated
again as a new speech channel.
The method and the apparatus of the present
invention have been described of the key telephone system
by way of example. Without being limited thereto,
however, the present invention can be applied to home
telephone systems or PBX systems. Further, the present
invention can be applied to an independent cordless
telephone system. In this case, however, the function of
designating a channel to be used is provided for the CE,
instead of the KSU.
