Note: Descriptions are shown in the official language in which they were submitted.
~3723~
~I~'LE: ~LECOMMUNICA~ION SYS~M I~CORPORA~ING
POR~ABIE COMMU~ICA~IO~ UNI~S
~ `he present invention relates to telecommunications
systems and is more particularly concerned with.improving
the facilities currentl~ provided by public call-office
kiosks and the like.
During recent years the telepho~e system has been
expanded to allow data communication to be added to speech
communication between subscribers. ~uch data com~unication
facilities, however, have had limited penetration, as far
as the total subscriber's on a national telephone network
is concerned, mai~l~ because relatively expensive modem
and hard copy printer and ke~board communication equipment
is required at each end o~ a communication connection. In
the main people are, however, periphatetic and it is
necessar~ for communication system~ to recognise that
subscribers require to make telecommunicatio~ caIls as they
move around from their natural ba~e, for example as they
travel from home to office, travel away on business or on
holidayO At present7 however, onl~ a few people with radio-
telephone equipment can actually take their communication
equipment with them. ~or the remainder public call offices
and renters pa~-phones must suffice.
According to the invention there is provided a
telecommunication s~stem ha~ing a pluralit~ of communication
terminals connected to the switching network of the system,
each communication te~minal being arranged to co~operate
with a pluralit~ of portable communication units each of
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37i~3~
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which is adapted to co-operate with a~ of the communication
terminals to set-up telecommunication càlls involving the
network to netwoxk terminations and each portable communication
unit includes a call tariff charging arrangement adapted to
be used to account for the usage of the portable communication
unit o~ chargeable telecommunication calls involving the
network.
~ he present in~ention envisages a telecommunication
system ha~ing a pluralit~ of subscribers terminals and a
10. pluralit~ of communication terminals connècted to the
networ~ of the s~stem, each communication terminal is
arranged to co-operate with a pluralit~ of portable
commu~ication units a~d each portable communication unit
` i9 adapted to co-operate with any of said communication
terminals to set-up telecommu~ication calls i~volving the
. network and a portable communication unit to a~y of the
subscribers terminals on the network and each portable
communication u~it includes means for coupling the portable
communication unit to a communication te~minal, means for
txansmitting telecommunication network control information
and communication informatio~ to a commu~ication te~minal,
mea~s for receiving telecommunication information from a
commllnication terminal and telecommunication tariff credit
metering arrangements adapted to decrease the telecommunica-
tion call charge credit of the handset in accordance withthe telecommunication call usage of the handset and each
communication terminal includes means for inter~acing the
portable communication units with the telecommunications
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network including mea~s for receiving telecommlln;cation
in~ormation from a portable communication unit and means
~or transmitting telecommunications information to a
portable communication unit.
In one embodiment of the invention the co~munication
terminal unit includes means for computing tarif~ credit
metering adaustment information from the network tariff
metering informatio~ and means for communicating the
adjustment information to the portable communications unit
to modify the contents o~ the credit metering arrangement.
In a simple interpretation of the invention individual
users of the arrangement are provided with portable
telephone units which are physically similar to a pocket
calculator and include a telephone transm~tter, receiver,
key pad unit and call credit store. ~he portable communica-
tion unit is arranged to co-operate with the communication
terminal, coupling between being by radio, inductive loop,
optical radiation, ultrasonic coupling, hard wire ccupling
or the like~
I~ order to make a telecommunications call, the user
positions himsel~ within some standard distance, say
five meters, of one of the communication termi~al and then
op~rates his portable communication llnit to gain access to
the telephone system to make a telephone call. ~he
communication terminal ma~ be mounted at any convenient
position whether on a post, wall or roof for example.
~he communications terminal need be o~ small size and is
arranged to operate unattended. It ma~ be hidden behind a
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~37239
facade say three meters above ground level and marked with
a logo such as "phone point". Accordi~gl~ the communications
terminal occupies little or no space, as compared with the
conventional kiosk and is not accessible to vandals. ~he
portable telephone unit comprises a push-button key pad
for dialling, a displa~ device and an integral earpiece
together with a microphone which for example is extendable
to the normal spacing from the earpiece using an acoustic
tube. ~ccess to the telephone s~stem is gained by touching
a key code sequence on the poxtable telephone unit, when
the user is within range of the terminal unit. When access
is confirmed, the user keys in the standard area code plus
the required telephone number and when the call is established
the communication terminal indicates cost information over
the reverse communication link to the portable telephone
unit~ ~he credit meter arrangement is amended by this
i~formation.
In more extensive interpretations a poxtable
commu~ications unit ma~ be arranged to incorporate the
equipment nece~sary for the setting-up of data communication
connections with the portable communication u~it including
a data modem, hard copy pri~ter and keyboard in addition
to the call tariff metering arrangementr In such circumstances
the communication terminal will act as a normal telecommunica-
tions connection interfacing the portable communication unitto the telephone network. Alternatively the communication
terminal may be provided with the modem facility and the
portable communication unit with the printer and keyboard
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~372~
facilit~ only in addition to its call tariff metering
arrangement and normal telephone connection ~acilities.
Each communication terminal is arranged to provide
telecommu~icatio~ facilibies for a number of portable
communication units allowing simultaneous commlln;cation
calls to be in being at the same timeO Combinations of
differing types of telecommunicatio~s calls involving voice
communication and or data communication will be handled
by the communication terminal. ~he communication terminal
10 - unit is arranged to handle for example eight communication
chPnnels and is provided with one common control chPnnel.
~he common control channel is used to set-up the initial
connection between a "calling" handset and the termi~al
u~it which, upon vaIidation of the interchauge between
the handset and terminal unit, allocates one of the communica-
tion ch~nnels which is used thereafter for telecommuLication
signalling and communication purposes for the duration of
the call~
~n addition the communications terminal ma~ also be
provided with so-called "teletext" or "view data" facilities
allowing a subscriber with a portable communications unit
incorporating the necessary interrogation facilities to
~se~
communication with the Pr~~,-Or~CT~ a~d CEE~A~ systems
as required.
~urther the communication ter~inal may be provided
with store and forward facilities allowing messages to be
stored for passage to a busy subscribers terminal at a later
date. ~picall~ store and forward messages could be held
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_
in the communication terminal for transmission outside
the busy periods of commuDication activity allowing the
recorded message to be sent at the low tariff rate after
having being recorded during a higher tariff rate period~
Under such circumstances the communication terminal will
compute the lower tariff and arrange for the credit store
arrangement in the portable communication unit u~ed in
making the recorded message to be adjusted accordingly.
~ypically the credit store arrangement comprises a
programmable read only memory and tariff information
I communicated from the communication terminal is used to
! erase the credit progressively from the memory~
I ~he portable communication unit is arranged to include
a display device, typicall~ of the liquid crystal type,
t 15 which may be used to indicate the cost of an individual
telecommunication call and the amount of credit left in
the portable communication unit. In addition the displa~
may be used to in~icate the telephone nùmber dialled to
validate the integxity of the reverse link betwee~ the
i 20 portable communication unit and the commu~ication te~minal.
~he invention, together with its various features
will be more readily understood ~rom the following description
which should be read in conjunction with the aCcQmpa~ying
drawings. Of the drawings:-
Fig. 1 shows in block diagram form, the equipment
necessary ~or the handset or portable communication unit,
Fig. 2 shows in block diagram form, the equipment
necessary fox the "phone point" terminal or communication
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terminal,
~ ig. 3 shows the radio frequency stability control
section of the portable commum cation unit,
~ ~igo 4 shows a flow diagram of the operations performed
b~ the h~ndset in the execution of a call whereas
Fig. 5 shows a flow diagram of the operations performed
b~ the phone poin-t terminal in the handling of a call.
In the following description the handset refers to the
portable communicatio~ unit whereas the phone point terminal
refers to the communication terminal.
Before embarking upon a detailed discussion of the
e~uipment used in the handset and communication te~minal
unit of the invention con~ideration will be given to the
overall new telecommunication s~stem ~acilities which may be
provided by the e~uipment of the invention. Hereafter -the
new s~stem will be referred to as phone point. ~he two
maaor elements of the phone point s~stem are (i) a portable
teIecommunications handset incorporating a micro-processor
which controls the handling o~ telecommu~ication calls a~d
the accountancy for those calls and-~ii) a communication
-terminal also micro-processor controlled and arranged to
handle a number of handset calls at any one time and to
interface the handsets into the normal telecommunication
network conmunicating call accountancy information to the
handset communication with the terminal. ~gpically the
handset comprises a minature push-button telepho~e instrument
of the size of a pocket calculator which includes a display
device, a micro~processor, a credit store memo~, a
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1~37;~;~9
telecommunication transmitter and receiver and equipment
for co~municating with the terminal unit. ~he handset
when not in operation ma~ be folded up so that it ma~ be
carried in a suit pocket or handbag. When it is required
to use the handset it is opened up so that it forms a
telephone instrument handset. ~he terminal unit of the
phone point system is used to interface the handsets to
the normal telecommunication network.
~ypically the phone point terminal ~lnits are provided
in public places such as airport terminals, railway stations,
theatre foyers1 shopping precincts and the like in a
similar manner to present day telephone kiosks. ~owever
the phone point terminal unit is not equipped with a
telephone instrument handset or coin collecting equipment.
Subscribers to the phone point system are allocated their
own portable handsets which in the simplest interpretation
of the phone point system include a telephone call credit
store. A subscriber wishing to make a phone point call
simply positions himself within a short distance~ say
5 meters, of a phone point terminal unlt and uses his
handset to set-up a telephone call by way of the phone point
te~minal unit.
Commu~ication between the handsets and each phone point
terminal unit involves radio com~unication involving
microwave communication links. ~ach phone point terminal
is provided with one common control chAnnel and eight
communication channels. lhe common control ch~nnel is
used during initial set-up between a handset and a phone
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point terminal unit before an available communication
cha~nel is allocated ~or use on a telephone call. During
a telephone call the call credit memory in the handset is
adjusted i~ accordance with the cost of the ~elephone call
made. At the end of the call the subscriber may control
the handset micro-processor to operate the handset display
to indicate the total cost of the completed call and the
remaining credit in the credit memory.
~ach phone point terminal unit is arranged to handle
concurrentl~ a number of phone point calls and the terminal
unit incorporates equipment for interfacing the so calls
to the telephone network.
~ rom the above it can be see~ that the pho~e point
system is analogous to present day telephone kiosk systems
but with the particular added advantages of enhancing
service availability, using the network more efficiently
and providing isolated call accountancy management. The
service availability is enhanced because the intrinsic
total terminal capital cost is lower since each terminal
can be used by a number of subscribers simultaneousl~.
~etwork utilisation is increased because of the ease of
use of the terminals-and concentration o~ facilities and
because of the simpli~ied credit/cash management system.
~he use o~ a credit memory in each handset which retains
either the level of credit purchased in advance by the
subscriber or by direct debiting by a central charging
system improves the telecommunications administrations cash
flow and removes the security hazard presented by cash-
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~37~39
boxes in telephone kiosks.
Consideration will now be given to the equipment used
in a handset and a commlLnication terminal unit in the
phone point s~stem.
~he handset equipment is ~hown in ~ig. 1 and consists
of a liquid cr~stal displa~ device HICD, a push button
ke~board HE, a micro~processor based operation control
system ~M-C, a call credit store ECS, a telephone instrument
transmitter H~ and receiver ~R and a low power crystal
controlled radio link HRE~/K~ which handles di~ital
information derived from speech using pulse code modulation
techni~ues involving the codec ~C and~the digital tra~smitter-
receiver H 9~-R.
~ ~ is operated
under micro-processor control to display the following
information:- telephone ~umber dialled, stored number,
messages credit remainin~ in credit memor~, cost of current-
call, time and date, queùe number and channel identification.
The stored number displa~ allows the handset to be
operated as a limited repertory dialling device allowing
the recall of one of sa~ ten stored telephone numbars~
~he message indication is used to provide in~ormation to
the handset subscriber such as (i) no credit, (ii) transmitter
fail (iii) te~minal fail, (iv) out of`~ of terminal,
(v) queue position, (vi) date/time error. ~inally the
channel identification information is used for identif cation
purposes for call back. It should be noted that as the
handset sto~es time and date it can be used as a tariff
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- 12 -
computer. ~he terminal unit will also know the date and
time and hence can confirm the accuracy of the handset
information be~ore accepting a call.
~he ~ush-button keYboard HE is used to enter dialled
informa-tion and operating instructions into the micro-
processor control system. In addition to the standard
digit buttons (0-9) for use in telephone push-button
dialling the keyboard is used to enter a user code and to
control the display device EICD in addition to providing
emergency calls,~a~da~ ~acilities and the controlling of
, a signalling tone (bleep) and back space and clear-
I operations when entering dialling or facility selection
! informationO ~he keyboard is used to enter the required
telephone ~umber (typicall~ country code, area code and
called subscribers number) usi~g the push-button switches
which are labelled 0 to 9 and presented in the standard
push-button dial formation. In addition the keyboard has
a user code key which when operated causes the handset
identity to be sent to the phone point terminal. ~he
handset identity is held in a read-only memory section of
the micro-processor~M-C. ~he ke~board also includes a
dial-out ke~ for use in controlling dialling and on
- repertory dialling operations o~ the handset, a mayda~
key allowing the handset to be used by an incapacitated
person for alarm purposes, call cost and credit left
display co~trol keys and call back, terminate, bleep on-off
and display clear a~d backspace keys.
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~3723
3 _
~ he handset micro-~rocessor ~M-C provides the ha~dset
function control facilities and its operation and
performance will be described in more detail later in
connection with ~ig. 4. ~he micro-processor operations
are initiated by information from the keyboard XE and the
digital receiver HD~/R and it controls the display ~ICD,
the credit store ~CS and the digital t~ansmitter/receiver
HDq!,/R ' ' '
~he flnal section of the handset involves the equipment
used to pro~ide the communication between the handset
microphone EM and receiver HR a~d the phone point terminal.
- ~his equipment involves a radio frequency link ha~dling
speech in p.c.m. encoded form. As mentioned previously
the radio li~k is controlled by a low power crystal oscillator
and operates at 100 M~z and p.c.m. encoding techniques
are used to modulate the radio frequency links. ~he micro-
wave link re~uires that the local oscillator in the ha~dset
be a~ stable as possible. ~ig. 3 shows the block diagram
of the wa~ in which the local oscillator is locked onto
the incoming signal from the phone point terminal with a~
appropriate of~set for the receiver I.~. ~he arrangement
of Fig. 3 consists of an image reflection filter IRF fed
from the handset aerial HAE. ~he output from the image
reflection filter is used to drive a radio frequency
amplifier RFA whose output is mixed in mixer M~ with the
output from the local oscillator ~0. l'he mixed signal,
after I~ filtering (in filter I~F) a~d amplification,
(in the I~ amplifier IFA) is fed to the digital transmitter-
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receiver HD~/R of ~ig. 1 after being demodulated by
demodulator DEM. ~he I~ amplifier output iq also used
to provide a feedback voltage si~nal proportional to frequenc~
from the converter ~C to control the differential amplifiers
OAR and OAS which derive the control signal to the local
oscillator IO. Initial acquisition upon switch-on of the
handset is performed automatically b~ sweeping the
receiYer over the lOO MEz band using a saw-tool search
waveform on the lead SW to control the search differential
amplifier OAS. ~he possibilit~ that a ~on-phone point
terminal transmitter mi~ht ~e incorrectly acquired is
dealt with by the micro-processor EM-C which will reject
signals having the wrong modulation and cause a search
to be continued.
~he output and input paths to the radio frequency
transmitter/receiver HRF ~/E~ are controlled b~ the digital
.
transmitter-receiver HD~/R which extracts the incoming
p.c.m. encoded speech for application to the codec HC
and thence to drive the handset receiver HR. ~he digital
transmitter-receiver is also used to allow micro-processor
generated i~formation to be passed to the radio frequency
transmitter or the handset receiver ~R. ~n example of the
latter is in the generation of an alarm tone (called a
"bleep") to alert the subscriber to a display condition.
~he function of the digital transmitter-receiver is
basicall~ to interface the radio frequency transmitter/
receiver to the codec EC and the micro-processor HM-C.
~he codec EC is used to convert the speech produced
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b~ the handset microphone ~M into p.c.m. encoded form and
to convert the p.c.m~ encoded information produced by
the di~ital transmitter-receiver HD ~/R into speech to
drive the handset receiver ~R. ~ypically the codec used
ma~ be that produced by Motrola under code number MC 3418
~he credit store ECS is used to provide each handset
with the facility for paying for the telephone call without
a cash transaction at the time of making the call~ ~he
contents of the credit store is arranged to be decremented
only by the action of the micro-processor ~M-C. ~he credit
store is ma~ufactured in such a way that it canno-t be
j reproduced or refreshed b~ the use of e~uipment available,
` even with difficulty, to the general public~ ~he credit
i store CS uses a derivative of the fusible link programmable
memor~ (PROM)~ In the P~OM device an array-of 4,000
I memory cells is formed on a single chip o~ silicon and
j each call is connected to the output circuits of the
memory chip ~y wa~ of a fine metal link~ In the non-
; programmed state the memory when read electrically has
1 20 4,000 cells set to the '1' state. I~ order to program
the memory short pulses (of the order of lOu ~econds) of
current are applied to the metal links connected to the
c~lls which it i~ required to set to the logical 'O'
condition. ~hese pulses o~ current fuse the metal links
and destro~ the connection to the output circuits. ~he
energy reauired to ~use a link is on the order of lOOu
Joules which is provided by a battery used to power the
; handset. After each phone point call the micro-processor
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~L~L3~239
- 16 -
HM-C computes the call charge and causes the necessary
~used li~ks to be disrupted to delete that credit value
from the credit store. ~ new PROM is installed into the
unit when the previous credit lèvel is exhau~ted; typically
a 4,000 bit capacity cartridge with a charging rate of say
3p per unit would provide a credit capacity of ~120.
~ he phone Point terminal unit is shown in ~ig~ 2 and
it consists of a micro-processor control system ~M-C,
a message store MS, a radio ~requency transmitter ~R~ and
a radio frequency receiver ~RFR~, a digital transmitter--
,receiver ~D~/R, a codec ~C and a telephone network 1ineinterface UDit ~1.
~ he te~minal micro-processor ~-C provides the
terminal UDit control facilities and its operation and
performance will be described in more detail later; in
co~nection with ~ig. 5. ~he micro-processor normally
functions in a background mode looking for a calling
h~ndset or a~ incoming call from the P~ network ~0 In
addition the micro-processor ~M-C is provided with an
emergency input EI which ma~ be used to cause the micro
processor to respond to the activatio~ of an emergency
button on the phone point terminal to handle Police, ~ire
or Ambula~ce calls originated without a phone-point'
handset. Associàted with the micro-processor ~M-C is
a message store MS which is used (i) to qtore messages
generated by handsets which have used the phone point
-- system to ~et-up a call to a busy telephone system subscriber
and (ii) to stoxe messages ~or phone point handset subscribers.
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~37239
The micro-processor is also provided with a dialling
information path DI for use in setting-up a telephone
call from the phone point terminal to a telephone subscriber.
Communication between the handsets and the micro-processor
in the termlnal unit involves the radio frequency links
and the digital transmitter receiver. Finally an alarm
device AD is associated with the terminal unit micro-
processor to indicate that there is an incoming telephone
system call waiting at the terminal unit.
I~ ~ig. 2 there is shown a broken line box referenced
Pæa~ and this indicates that a number of communication
channels are provided at a terminal unit and each
communication channel e~fectively has the use of equipment
shown within the box PPC~ addition the radio frequency
receiver ~R~R~ is used to listen ~or a control channel
request signal and the micro-processor ~M-C will commu~icate
with the "calling" phone point handset using the digital
transmitter-receiver ~D~R and the radio ~reauency trans-
m tter ~R~
- 20 ~o more readily u~derstand the operation of the phone
point system the interaction of a ha~dset and the terminal
unit will be co~sidered by following the actions of
these equipments in the e~ecution of a simple phone point
call. ~igs. 4 and 5 show the flow diagrams of the operations
performed and these figures will be used to aid the
understanding of the operations reauired.
~ig~ 4 shows the operations per~o~med by the handset
whereas ~ig. 5 shows the operations performed by the phone
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point terminal unit. ~he following description will be
sectloned under the headings of the steps shown in ~igs.
4 and 5.
~à initiate a phone point call a phone point subscriber
positions himself within a short distance from the phone
point texminal unit a~d opens the case of his handset.
Step SHl - Case oe_~_handset on
l'he opening o~ the handset case causes the power to
the ha~dset equipment to be switched on and an automatic
routine is entered involving step ~H2 to 8 to "connect"
the handset with a communication ch~nnel of the terminal
U~it.
~tep SH2_- ~erminal_sig~al level satisfa~
I~ this step the local oscillator looks for the phone
poi~t terminal transmitter and the micro-processor tests
the sig~al level generated at the output of the digital
t~ansmitter-receiver HD~/R of ~ig. 13 If the signal level
is not satisfactory the micro-processor produces a
p.c.m. code which is fed to the digital transmitter/receiver
HD~/R and the codec HC to cause a bleep tone to be produced
b~ the handset receiver H~ and the display HICD is driven
by the micro-processor to indicate that the signal level is
unsatisfactory and a pho~e point communication can not be
set-up. If the terminal signal is satisfactor~ step ~3
is performed.
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In this step the operations defined in ~ig. 3 are
performed to lock to local oscillator ~0. Of the handset
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~L3723
_ l9 _
to the frequency of the terminal. ~he micro-processor
controls the application of the search waveform SW of
~ig. 3 until the local oscillator is s~nchronised. If
synchronisation is not achieve~ again a "bleep" warning
is generated and the handset~displa~ is activated to indicate
a s~nchronisation failure. Alternatively when the handset
- local oscillator has been synch~onised with the terminal
carrier~ Step SH4 is performedO
Step ~H4 - Check Control Channel
In this step the micro-processor conditions the
digital transmitter receiver HD~R to extract the information
f~om the received signal from the terminal unit corresponding
to the common con~rol channel. As mentioned above the
phone point terminal unit handles a number of communication
channels and common to all these GommUniCation channels is
one control channel which is used only during the initial
period of a phone Point call by a handset until a communica-
tion channel is allocatedO
In this step the common control channel extracted by
the digital transmitter receiver HD~/R is tested to see i~
it is f~ee. I the commo~ control channel is not free
(i.e. a~other ha~dset is setting-up a phone point call) the
handset remains in the loop provided b~ steps SE4 and SH5
u~til the channel is free when step SH6 will be performedO
~ ' .
In this step the micro-processor HM-C inserts into
the control cha~nel, b~ way of the digital transmitter and
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the transmitter part of the radio frequency link, a request
communication channel code. ~his code will be passed to
the phone point terminal where it will be detected to cause
entry into the phone polnt ~erminal call set-up procedure
shown in ~ig. 5.
Ste S~l - Is Communication Channel available
I~ thisstep the micro-processor ~M-C will detect,
using the digi~al transmitter receiver I9 I/R that a
communication request has been received on the common
channel and it tests to see if there is a free communication
channel available. If there is not step S~2 is performed
whereas step SI3 is performed i~ there is a free communication
~¦ cha~nel available.
-¦ Step ~2 - Send Queue ~umber
! 15 In this step the terminal micro-processor ~M-C
j inserts into the control ch nnel~ through the digital
! transmitter-receiver ~D~/R, informa~ion indicative of the
number in the queue the calling handset has been allocated.
~his information having been sent to the calling handset-
over the commou channel will cause its step SE7 (~ig 4
to be exited by way of the "no" path whereas the phone
point terminal-will return to a background program awaiting
; demands or information from other handsetsO
Ste~ S _-_Communication Cha~nel available?
In this step of the handset program the reception of
the queue number over the common ch~nnel will cause a
"bleep" to be generated in the handset receiver HR and
the queue number allocated by the terminal (in step S~2
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~37239
above) will be displayed on the display HICD.
Step SM8 - Wait 5 seconds
In this step the program is suspended awaiting a five
second time out before repeatin~ steps S~4, S~5, SH6, SE7
and SE8 etc. until step SH7 ca~ be exited u~ing the "yes"
path. ~or each entry into step S~6 an entr~ is made into
step S~l in the phone point terminal. Ultimately there
will be a communication channel available and the terminal
will execute step S~3.
Step S13 - Send Communication Channel number
I~ this step the micro-processor ~M-C injects into
the contxol channel, using the digital tra~smitter-receiver
~D~/R in~ormation indicative of the number of a commlln;ca-
tion channel allocated to the callin6 handset. ~he terminal
unit now enters the loop formed b~ steps S~4 and S~5 awaiting
for the dial information from the calling handset.
In this step the output from the digital transmitter
receiver D~/R for the commu~ication channel allocated to
the c~lling handset is interrogated.
In this step the information derived from the channel
-~ allocated to the calling handset is tested by the micro-
processor ~M-C to see if it is ~e&~g informatio~ if it is
not then step S~4 is re-entered~
~ he performance of step S~3 by the terminal will cause
step SE7 in the calling handset to be exited on the "~es"
path into step SH8 (of ~ig~ 4).
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Step ~H8 - Set Eandset to ~llocated Channel
~his step i9 entered because the micro-processor
will have detected the reception of the communication
ch~nnel identity in the commo~ channel produced by the
digital transmitter/receiver ~D~/R output.` ~he reception
of the communication chpnnel identity causes the micro-
processor to condition the radio-frequency transmitter~
receiver HRP~x/R~ to adjust its radio frequency circuit
to set to the allocated commuDication ch~nnel. At the same
time the digital transmitter receiver ED~/R is conditioned
to produce a "bleep" in the handset receiver HR and the
display device ~CD is operated to indicate "start dialling".
~he phone point subscriber ~ow starts dialling the number
he requires usin~ the push-button ke~board HE to enter
the required telephone number into the micro-processor HM-C~
Step SH9 - Store a}~L~g}~gy~ a~formation
~he micro-processor is arranged to receive the dialled
information ~rom the keyboard HE and to display the telephone
number so compiIed. Upon completion o~ the dialling
information the handset waits for the dial-out com~l~nd ke~
o~ the keyboard HE to be operated. ~his allows the
subscriber to check that he has keyed in the required
telephone number correctly.
Step SH10 - Dial out comm ~
In this step the operation of the dial~out command
key is tested for. If it is not operated step SHll is
performed to clear the di~lling store in the micro-processor
~M~C and to ca~cel the information on the displa~ HLCD.
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~113723
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When the dial-out command is received Step SHl2 is per~ormed.
Step S~2 - Send number_out over link
In this step the micro-processor ~M-C injects the
di~lling information into the allocated communic~tion
ch~nnel using the digital transmitter-receiver ~D~/R. ~his
dialling information will be passed over the allocated
commun'cation channel lnvolving the microwave link between
the handset and the termi~al and step S~5 ~Fig. 5) will be
~ exited using the "yes" path.
i lO Step S 6 - Buffer dial information to network
In this step the received dialling information is
¦ received by the micro-processor ~M-C from the allocated
communication channel by wa~ o~ -the digital transmitter-
receiver ~D?/R. As the dialling information is received
1 15 the micro-processor ~M-C converts that information into
~ suitable form for transmission to the telephone network
', a~d this converted information is passed over lead DI to
the line interface equipment of the telephone network line
corresponding to the allocated channel~ ~he terminal will
circulate in steps ~6 and S~7 u~til the di311ing out over
the line interface is complete. Eaving sent the dialli~g
information out over the communication channel the handset
performs step SHl3.
In this step the micro-processor ~M-C connects the
digital transmitter receiver HD~/R through to the codec EC
thereb~ connecting the handset microphone ~M and receiver
; ~R through to the allocated communication chPnnel. At the
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same time the terminal will have completed its dialling-out
operation entering step S~8 (~ig. 5).
Step S~8 - Establish Audio,_path
In this step the micro-processor ~M-C will connect
the allocated communication channel to the line interface
~I serving that telephone network termination taken into
use by the micro-processor ~M-C to repeat the dialling
information~ ~his.makes the "audio" path from the line
inter~ace through to the handset microphone ~M and receiver
ER. ~he terminal now returns -to a background program
allowing other phone point calls to be serviced. ~he rest
of the c 1-1 until it is termi~ated will be administered
b~ the handset performing steps SHl4~16.
Ste ~
15 In this step the micro-processor H~-C will detect the
set-up of the telephone call (i.e. when the called sub
answers). ~his i9 used to start the accounting function
for the caIl. ~ypicall~ the micro-processor EM-C in the
handset knows the called ~umber and it knows the time oX day
so it ca~ start mo~itoring the call loo~ing for a call
term~nate co~dition to be able to calculate the cost of the
call to be deleted from the credit store ECS. ~hese steps
are shown i~ ~i30~. 4 at ~Hl4, SHl5, SHl6 and S~17.
~he micro-processor HM-C will record the time of day
at which this occurs and wlth reference to the ~umber dialled,
it can calculate the cost o~ the call in accordance with
internall~ store call charges~ ~ call termination ma~ be
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as a result o~ the Subscriber ~olding up his handset or
operating the call terminate button or the keyboard HE.
Ste~ SH17 - Decrement credit store
In this step the call cost calculated in steps SRn5
and 16,is decremented from the credit store ~C~. ~his
terminates the operation of the phone point s~stem eauipment.
~he above description has been o~ one simple embodiment
,only and is not,intended to be limiting to the invention.
Many alternative arrangements can be envisaged by those
skilled in the art, for example the above description has
indicated that the credit store is decremented in accordance
, with an internal calculation performed b~ the micro-processor
of the handset. An alternative arrangement could be provided
where the phone point terminal generates metering information
~` 15 which is communicated over the allocated communication
channel to the handset. Further the flow diagram of ~igs~
4 ,and 5 are necessaril~ brief and many routes allowing for
call abandonment have not been shown~ Purther to validate
the phone point system an automatic interchange can be
included in the initial p,hone point system call set-up
procedure involving the ~ndset intarnal identity in~o~mation
exchange and the checking of the handset internal cloc~/
date mechanism. ~inally the way the phone point terminal
inter~aces to the telephone system obviously depends upon
the telephone system involved. ~ypically one line interface
may be provided for each netwGrk termination or a single
termination may be time division multiplex shared by a
number of phone point ch~nnels. Finally a "credit card"
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s~stem co~d be u~ed in place of the credit store with
the card number permanentl~ in the hand~et and with
central call accounting performed using information on
the call and credit card number located in the phone point
terminal.
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