Note: Descriptions are shown in the official language in which they were submitted.
2140680
The present invention relates to a portable telephone
set and, more particularly, to a portable telephone set
having a ringing circuit and to be used in a portable mode
and mobile mode.
This application is a divisional application of
Canadian patent application serial No. 2,035,411 filed on
January 31, 1991 claiming a convention date of January 31,
1990 .
There has been known a portable telephone set which
has two use-modes, i.e., a portable mode in which the
telephone set is used by a user while bringing it with
him and a mobile mode in which it is mounted on a vehicle.
In the portable mode, a compact and light-weight, built-in
loudspeaker is used. In the mobile mode, a relatively
large external loudspeaker is used because the loudspeaker
outputs not only a ringing tone but also a voice signal
and thus the voice quality therefrom plays an important
role.
In general, in the above-men.ioned ringing circuit,
the built-in, i.e., internal loudspeaker is compact and
has a narrow frequency characteristics while the external
loudspeaker has a relatively wide frequency characteristics.
In the conventional ringing circuit, however, a ringing
signal having a single frequency spectrum is used. Thus,
when the frequency characteristics of the internal and
external loudspeakers are different, there may be a
problem that the energy of a ringing signal for driving
*
- 2 ~ ~`6~ 0
the loudspeaker cannot be used effectively. More
definitely, when the ringing signal spectrum is broad
and the internal loudspeaker is used, a portion of the
frequency spectrum of the ringing signal which is not
used increases and the power consumption of a ringing
signal generating circuit is undesirably increased.
On the other hand, when the ringing signal frequency
spectrum is narrowered to adjust it to the internal
- loudspeaker, it is impossible to supply enough power
to the external loudspeaker, so that an effective
ringing sound cannot be generated.
Furthermore, the switching between the internal
and external loudspeakers is manually carried out.
This manual switching is a troublesome operation for
the user.
SUMMARY OF THE INVENTION
An object of the present invention is, therefore,
to provide a ringing circuit for use in a portable
telephone set which circuit is capable of producing
an effective ringing sound for either an internal or
external loudspeaker thereof to be used.
Another object of the present invention is to
provide a ringing circuit for use in a portable telephone
set which circuit automatically switches internal and
external loudspeakers based on the use conditions of
the portable telephone set.
~ 3 214Q680
According to the present invention, there is provided
a portable telephone set having two use-modes, portable
mode and mobile mode, and includes a mode detecting
circuit for detecting the use-modes. Upon a call
S frcm a base station, a ringing circuit of the portable
telephone set generates ringing sound from an internal
loudspeaker thereof when the portable mode is detected
or from an external loudspeaker when the mobile mode
is detected. In the portable mode, the ringing circuit
produces a rirst ringing signal havlng a frequency
spectrum adjusted to frequency characteristics of the
internal loudspeaker and, in the mobile mode, produces
a second ringing signal having a frequency spectrum
adjusted to frequency characteristics of the external
loudspeaker. The ringing circuit may include two
ringing sisnal generating circuits which generate
the first and second ringing signals, respectively.
Further, the ringing circuit may include a single
ringing signal gener2tinS circuit which generates
the first or second ringing signal depending upon
use-mode detected. When the external loudspeaker is
connected to the telephone set, an input terminal of
the mode detecting circuit is grounded simultaneously
and this grounding signal can be used as the detection
signal of the mode detection circuit.
21~0680
BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other objects, features and
advantages of this invention will become more apparent
by reference to the following detailed description of
the invention taken in conjunction with the accompanying
drawings, wherein:
Fig. 1 is a schematic block diagram showing a
portable telephone set according to an embodiment of
the present inventioni
Fig. 2 is a flowchart explaining the call reception
operation of the Fig. 1 portable telephone set;
Fig. 3 is a schematic block diagram showing a
specific construction of speaker/microphone of the
Fig. 1 embodimenti
Fig. 4 shows frequency characteristics of an
internal loudspeaker and an external loudspeaker which
are used in the Fig. 3 embodiment;
Fig. 5 is a schematic block diagram showing a
ringing tone generator of the speaker/microphone
portion shown in Fig. 3;
Fig. 6 is a schematic block diagram showing a mode
detecting circuit used in the Fig. 3 embodiment;
Fig. 7 is a schematic block diagram showing another
specific construction of speaker/microphone portion of
the Fig. 1 embodiment; and
Fig. 8 is a schematic block diagram showing a
- s 2140fi80
ringing tone generator of the speaker/microphone portion
shown in Fig. 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In Fig. 1, a portable telephone set 10 can be carried
by the user or mounted on a vehicle. The telephone set 10
has an antenna 1 picking up a radio grequency (R~ signal
and radiating an RF signal. The antenna 2 may be replaced
by or switched to a vehicle-mounted antenna when the
telephone set 10 is mounted on the vehicle. The picked-
up RF signal is supplied to a receiver portion 3 through
-an antenna duplexer 2. The receiver portion 3 demodulates
the received RF signal to produce an audio frequency (AF)
signal which may include a voice signal and a data signal.
The voice signal is supplied to a speaker/microphone
portion 5 to be outputted from a speaker circuit 12 or
a handset 14 therewithin. The handset 14 may include
an earpiece receiver and a mouthpiece microphone. The
data signal is supplied to both a call detector circuit 7
and a control circuit 9.
The speaker/microphone 5 includes a microphone
circuit 13 as well as the speaker circuit 12 and the
handset 14. The microphone circuit 13 and speaker
circuit 12 are used for the so-called hands-free
telephoning in which the user can make conversation
through these circuits 12, 13 without resorting to
_ - 6 21~0680
the handset 14. The hands-free telephoning can be performed
only when the telephone set 10 is mounted on a vehicle. In
this case, ~he speaker circuit 12 is used for conversation
and for generating an audible ringing tone. When the
telephone set 10 is used as a portable one, the handset 14
is used for conversation and the speaker circuit 12 is
dedicated to generating an audible ringing tone.
A voice signal is inputted through the microphone
circuit 13 or the handset 14 and supplied to a transmitter
portion 4. The transmitter portion 4 also supplied with
a data signal from the control circuit 9 and various
signals from a signal generator 6. The transmitter
portion 4 transmits the supplied signals to a base station
(not shown) of a mobile communications system through the
duplexer 2 and the antenna 1. The signal generator 6
generates the various signals under the control of
control circuit 9. The control circuit 9 also controls
the receiver and transmitter portions 3, 4, especially,
causes them to tune to a desired radio frequency channel
in a well-known manner.
The call detector circuit 7 detects from the supplied
data signal a calling signal addressed to the telephone
set 10 and produces a call detection signal. The call
detection signal is led to both the control circuit 9
and speaker/microphone circuit 5. In response, the
speaker/microphone circuit 5 generates an audible
~_ 7 2140680
ringing tone through the speaker circuit 12 to alert the
user to a call.
The telephone set 10 further includes a mode detect
circuit 8 which detects the use condition of the telephone
set 10. More specifically, if the telephone set 10 is
used as a portable set, the mode detect circuit 8 prcduces
a portable-mode signal. If the telephone set 10 is
mounted on a vehicle, the mode detect circuit 8 produces
a mobile-mode signal. Upon the mobile-mode signal, the
control circuit 9 may switch from the antenna 1 to the
vehicle-mounted antenna.
In response to the portable-mode signal, the speaker
circuit 12 generates a first audible ringing tone whose
frequency is suitable to an internal speaker accommodated
in the telephone set 10, which will be described later.
On the other hand, in response to the mobile-mode signal,
the speaker circuit 12 generates a second audible ringing
tone whose frequency is suitable to an external speaker
to be connected to the telephone set 10, which will also
be described later. Since the frequencies of the ringing
tones are so selected, it is possible to prcduce an
audible ringing tone at the m~imum level with the
minimum power consumption.
In Fig. 2, the portable telephone set 10 waits at
step Sll for a call meant therefor on a so-called paging
channel which is one of control channels for broadcasting
- 8 - 21~0 680
calling signals and various control signals from a base
station to portable or mobile telephone sets. If the
telephone set 10 receives a calling signal addressed
thereto at step S12 and detects it with the call detect
circuit 7, the control circuit 9 causes the signal
generator 6 to generate a response signal. The control
circuit 9 further causes the transmitter portion 4 to
transmit at step S13 the response signal to the base
station. Thereafter, the control circuit 9 checks at
step S14 ~f it receives a channel designate signal
indicating a designated speech channel. If the control
circuit 9 does not receive the channel designate signal
within a predetermined period of time, the operation
returns to step Sll. Otherwise, the control circuit 9
causes the receiver and transmitter portions 3, 4 to
tune to the designated speech channel at step S15.
Step S15 is followed by step S16 at which the use
condi ion of telephone set 10 is checked using the mode
detect circuit 8. If the set 10 is used as a portable
set, the speaker circuit 12 generates a portable-mode
ringing tone whose frequency is suitable to the internal
loudspeaker at step S17. When the set 10 is mounted on
a vehicle, i.e., used as a mobile set, the speaker
circuit 12 generates a mobile-mode ringing tone whose
frequency is suitable to the external loudspeaker at
step S18. Steps S17 and S18 are followed by step Sl9
- - 9 -2140680
at which the control circuit 9 monitors if it receives an
off-hock signal indicating that the user goes off-hook to
start a telephone conversation. If the off-hook signal
is not received within a predetermined period of time, the
telephone set 10 returns to the waiting state (step Sll).
If the off-hook signal is received at step Sl9, the
control circuit 9 performs at step S20 a connection process
in which the handset 14 is connected to the receiver and
transmitter portions 3, 4 in the portable mode while the
microphone circuit 13 and the speaker circuit 12 are
connected to the transmitter and receiver portions 4 and 3,
respectively, in the mobile mode. The completion of the
connection process allows the user to start a telephone
conversation at step S21.
In Fig. 3, the speaker circuit 12 included in the
speaker/microphone portion 5 comprises a first ringing
tone generator 31 for generating a first ringing tone
whose frequency is suitable to an internal loudspeaker 32
connected thereto. The speaker circuit 12 also comprises
a second ringing tone generator 33 for generating a second
ringing tone whose frequency is suitable to an external
loudspeaker 35. Between the second ringing tone generator
33 and the external loudspeaker 35 is connected a signal
combining circuit 34 for combining the second ringing
tone and a voice signal from the receiver 3 (Fig. 1).
The external loudspeaker 35 is to be connected to the
- lO - 214068~
signal combining circuit 34 through a terminal 36 attached
on a telephone set housing 37. While a voice signal is
outputted through the external speaker 35 together with
the ringing tone in the mobile mode, a voice signal is
outputted through the handset 14 (Fig. l) in the portable
mode. In the portable mode, only the ringing tone is
outputted from the internal loudspeaker 32.
As mentioned above, the frequency spectrum of the
first ringing signal produced by the first ringing tone
generztor 31 is set so that it substantially corresponds
to a relatively narrow frequency characteristics of the
internal loudspeaker 32. On the other hand, the frequency
spectrum of the second ringing signal generated by the
second ringing tone generator 33 is set so that it
substantially corresponds to a relatively wide frequency
characteristics of the external loudspeaker 35.
A connector 38 mounted on the housing 37 is connected
to the mode detecting circuit 8. The connector 38 is
grounded when the telephone set, i.e., the housing 37
is mounted on a vehicle. Thus, when the connector 38
is not grounded, the mode detecting circuit 8 detects
that the telephone set is in the portable mode while
when the connector 38 is grounded, the mode detecting
circuit 8 indicates that the telephone set is in the
mobile mode. The connector 38 may be constructed such
that, when the external loudspeaker 35 is connected
1 - 2140680
through the connector 36 to the signal combining circuit
34, it is grounded simultaneously. The mode detecting
circuit 8 provides a portable mode signal indicative of
the portable mode to the first ringing tone generator 31
and a mobile mode signal indicative of the mobile mode
to the second ringing signal generator 33. The call
detecting circuit 7 detects a calling signal from a data
signal from the receiving portion 3 and provides a call
detection signal indicative of the presence of calling
signal reception to both the ringing tone generators 31
and 33.
With the Fig. 3 construction, when the telephone set
is in the portable mode and there is a calling signal
reception, the first ringing tone generator 31 is operated
to send the first ringing signal to the internal loud-
speaker 32. In this case, since the frequency spectrum
of the first ringing signal corresponds to the frequency
characteristics of the internal loudspeaker 32, the first
ringing tone generator 31 can operate the internal loud-
speaker 32 effectively with minimum power and thus theringing can be performed effectively. On the other hand,
when the telephone set is in the mobile mode and there
is a calling signal reception, the second ringing tone
generator 33 operates to produce the second ringing
signal to the external loudspea~er 35. In this case,
since the frequency spectrum of the second ringing
- 12 - 214068~
.
signal corresponds to the frequency characteristics of
the external loudspeaker 35, the second ringing tone
generator 35 actuates the external loudspeaker 35 with
full power, so that it is possible to call with maximum
volume of the external loudspeaker 35.
Referring to Fig. 4, an example of frequency
characteristics of the internal loudspeaker 32 is shown
by a curve A and that of the external loudspeaker 35 is
shown by a curve B. These data were obtained based on
the output voltages of a microphone circuit which picks
up sound from the respective loudspeakers under the same
measuring conditions. In general, the internal loudspeaker
32 is compact and thus its sound generating efficiency
is better in a narrow frequency band. On the other hand,
the external loudspeaker 35 does not provide high sound
generating efficiency although it exhibits a good
frequency characteristics. The curve A indicates that
the internal loudspeaker has a sharp peak at 2.9 kHz
with its output level being about 5.2 dBV. The curve A
also shows that the internal loudspeaker outputs an
output level of about -1.5 dBV at 1.5 kHz and of about
-3.5 dBV at 1.3 kHz. On the other hand, the curve B
exhibits that the external loudspeaker has a relatively
wide frequency characteristics and its m~xi mum output
point is at 1.3 kHz with level being about 0 dBV. Also,
the external loudspeaker outputs an output level of about
- 13 - 2140680
. .
-7.0 dBV at 1.5 kHz and of -4.0 dBV at 2.9 kHz.
Setting the ringing signal frequency to a single
frequency such as 1.5 kHz which is the frequency of ringer
of a cable telephone, there is no problem for the external
loudspeaker 35 since its frequency at which a high output
level is prcduced is substantially coincident with the
ringer frequency. However, for the internal loudspeaker
32, its output level at the ringer frequency is lower
than the m~ximum output level by about 7 dB. When such
internal and external loudspeakers 32 and 35 are driven
by a ringing tone having such a single frequency, it is
impossible to operate the loudspeaker and the ringing
tone senerator efficiently in either the portable mode
or the mobile mode. However, when, as shown in Fig. 4,
the frequencies of the first and second ringing tones
respectively generated by the ringing tone generators
31 and 33 are set at around 2.9 kHz and around 1.3 kHz,
respectively, it is possible to use the loudspeakers
32 and 35 and the ringing tone generators 31 and 33
efficiently. Moreover, each of the first and second
ringing tones need not-have wide frequency spectra
and thus they can use a tone having a single frequency
spectrum.
In Fig. 5, each of the ringing tone generators 31
and 33 comprises an oscillator 51 for producing a ringing
tone, an oscillator power source 52 for supplying power
- 14 -21~ 0680
from a power source to the oscillator 51 and for on-off
operating the power source and an AND gate 53 for on-off
controlling the oscillator power source 52. To one input
of AND gate 53 a calling signal detection signal is
supplied from the calling signal detection circuit 7
and to the other input thereof a portable mode or mobile
mode signal is supplied from the mode detecting circuit 8.
When AND gate 53 receives these inputs, the gate 53 makes
the oscillator power source 52 turn on so that the
oscillator 51 produces the first or second ringing tone.
More specifically, in the first ringing tone generator 31,
AND gate 53 makes the power source 52 turn on when the
gate 53 receives the calling signal detection signal and
the portable mode signal. In the second ringing tone
generator 33, AND gate 53 makes the power source 52 turn
on when the gate 53 receives the calling signal detection
signal and the mobile mode signal.
In Fig. 6, the mode detecting circuit 8 comprises
a terminal 61 to which a positive voltage is applied.
To the terminal 61 is connected the one end of a pull-up
resister 62 the other end of which is connected to the
connector 38. To the connector 38 are connected the
inputs of inverters 63 and 64. The output of inverter
63 is connected to the input of an inverter 65 whose
output is connected to the first ringing tone generator
31. The output of inverter 64 is connected to the second
ringing one generator 33.
40680
In operation, when the connector 38 is grounded, i.e.,
the telephone set is mounted on a vehicle, the output of
inverter 64 becomes a high level indicative of the mobile
mode, while the output of inverter 65 becomes a low level.
Thus, only the second ringing tone generator 33 is enabled
to generate the second ringing tone. In contrast, when
the connector 38 is not grounded, i.e., the telephone
set is removed from a vehible, the output of the inverter
64 becomes a high level indicative of the portable mode,
while the output of inverter 64 becomes a low level.
Thus, only the first ringing tone generator 31 is enabled
to generate the first ringing tcne.
Fig. 7 shows another example of the speaker circuit,
denoted by reference numeral 12A, comprising a ringing
tone generator 71 which produces the first or second
ringing tone according to the use mode of the telephone
set. The output of tone generator 71 is supplied to a
signal combining circuit 72 to be combined with a voice
signal from the receiving pcrtion 3. The output of
combining circuit 72 is coupled to a speaker switching
circuit 73 which connects the output of signal combining
circuit 72 to one of the internal and external loudspeakers
32 and 35. The external loudspeaker 35 is to be connected
to the speaker switching circuit 73 through the connector 36.
Although the use mode signal outputted by the mode
detecting circuit 8 may include the portable mode signal
21~0680
- 16 -
and the mobile mode signal as described with reference to
Fig. 6, here, an output level variation of either of the
mode signals is utilized. The ringing tone generator 71
produces the first ringing tone when the use mode signal
is the portable mode signal and the calling signal
detection signal is supplied. The generator 71 also
generates the second ringing tone when the use mode
signal is the mobile mode signal and the calling signal
detection signal is supplied. The signal combining
circuit 72 combines the voice signal and the second
ringing tone when the use mode signal is the mobile mode
signal while it merely passes therethrough the first
ringing tone when the use mode signal is the portable
mode signal. The output terminal of the speaker switching
circuit 73 is switched to the internal loudspeaker 32 when
the use mode is the portable mode and to the external
loudspeaker 35 when it is the mobile mode. Therefore,
the ringing tone generator 71 of the speaker circuit 12
produces two kinds of ringing tone.
In Fig. 8, the ringing tone generator 71 is connected
through a bus 81 to the control circuit 9, which may
comprise a microprocessor, the calling signal detection
circuit 7 and the mode detecting circuit 8. The ringing
tone generator 71 comprises a clock generator 82 for
generating a clock signal. The clock signal is supplied
to a frequency divider 83 at which the clock signal is
17 21406~0
frequency divided. The divided clock signal is counted
by a counter 84 whose output is applied to a read-only
memory (ROM) 85. ROM 85 preliminarily stores patterns
corresponding to the first and second ringing tone
frequencies and provides one of the stored patterns
according to the output of counter 84. The output
pattern of ROM 85 is supplied to a D/A converter 86
which converts the supplied patterns into a sinusoidal
wave signal containing high harmonics. A low-pass filter
(LPF) 87 eliminates the high harmonics contained in the
output of D/A converter 86 to provide a basic sinusoidal
wave signal and an amplifier 88 amplifies the basic
sinusoidal wave signal.
The rrequency divider 83 divides the frequency of
the clock signal by a first frequency-dividing ratio
when the portable mode signal is supplied from the mode
detecting circuit 8 and the calling signal detection
signal is supplied from the signal receive detecting
circuit 7. On the other hand, when the mobile mode
signal and the calling signal detection signal are
supplied, the frequency divider 83 divides the clock
signal by a second frequency-dividing ratio. The
counter 84 is used as a decoder for assigning addresses
for ROM 85 and the output of counter 84 when counted with
the first frequency-dividing ratio reads the pattern
corresponding to the first ringing tone frequency stored
- 2140680
in ROM 85. On the other hand, the output of counter 8g
when counted with the second frequency-dividing ratio
reads the pattern corresponding to the second ringing
tone frequency stored in ROM 85. In this manner, the
two kinds o~ ringing tone can be digitally produced.
As described hereinbefore, the ringing circuit of
the portable telephone set according to the present
invention includes the ringing tone generators for
generating the first and second ringing tones whose
frequencies are set to be ~uitable to frequency
characteristics of the internal loudspeaker to be used
in the portable mode and of the external loudspeaker to
be used in the mobile mode, respectively. The ringing
tone is selected accordin~ to the use mode of the
telephone set in which the associated loudspeaker is
actuated. Therefore, it is possible to utilize the
ringing tone effectively in either mode and to provide
m~x; mllm ringing with mi ni mum power consumption.
