COIN TELEPHONE
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Requires a Subscribers Private Meter SPM supply and a signalling earth. Made by Landis and Gyr / Autelca AG (AZ33). An extract from Maintenance News 18, Spring 1981
Maintenance
thoughts on new coin boxes Most people are aware that a new generation of microprocessor controlled payphones will be progressively replacing the pay-on-answer ( POA) boxes. But few of those who have been involved with the maintenance of electro-mechanical POA boxes will mourn their passing. For introductory purposes the new range of payphones are divided into three tiers.
Another item in the new range is the Debit Card Payphone -Intended to accept specially designed credit cards. Tier 1 and the Debit Card Payphone are powered from external supplies whereas Tiers 2 and 3 will be powered from the telephone line. All require the services of Subscriber's Private Meter (SPM) equipment at the exchange but dispense with the need for a Coin and Fee Checking (CFC) relay set. The approach to fault finding and clearance is going to be very different from the POA coin box. Instead of coin acceptors, pulse units, runways and so on, the faultsman's language will be Central Processor Units (CPU). Speech and Interface (S and I) boards. Power Supply Units (PSU), credit displays, edge connectors and the like. Faultsmen will have a diagnostic kit to help them and, by using the diagnostic testing facilities built into the CT22. they will be able to approach their task in a truly professional manner. The recommended methods of handling this equipment particularly the printed Circuit boards are different from the accustomed practices of faultsmen. For example circuit boards with edge connectors must be extracted and Inserted only when absolutely necessary. They must be handled with extreme care, always carried in anti-static bags, and provided with adequate protective covering. In time faultsmen will need to become expert in the facilities, and capable of recognising the causes of the more common types of failure. This equipment should help create pride in the work, which most found difficult when working with POA apparatus. Faultsmen will still meet all the old situations and conditions that do little to help their task- kiosk windows broken or missing, customers anxious to use the box being worked on, noisy railway stations, bustling airport buildings and many others. This is an exciting challenge which faultsmen will be facing if British Telecom is to seize this opportunity to provide the type of PCO service the public demand. A first class maintenance effort is necessary even though these processor-controlled payphones are remarkably advanced machines. They must not be taken for granted. After working on a box. a faultsman must run though the facility test schedule and satisfy himself that all is as it should be. This includes a check to ensure that both the ear and mouthpieces are correctly fastened with rivets. Another point to remember is that most members of the public will initially find the new PCO's very strange and some may not be able to understand the instructions. Maintenance staff may be called upon by frustrated customers to explain, and this should be done in a way that will inspire confidence. No doubt some customers will expect to get coins refunded when they are not entitled to them. But the new call office mechanism does not give change, it only returns those coins not used during the call. For example, if a user puts one 50p piece into store, makes a call to the value of 10p, then hangs up, the machine will claim the whole of the 50p. But if at the end of the call. and before hanging up, the user inserts a further 10p piece, the payphone will claim the 10p piece and return the 50p to the user when the handset is replaced. Maintenance staff need to fully understand:-
There will be much for faultsman to learn during the early days of the new equipment. It will be very important when new problems or difficulties are found that help should be sought. They should also pass on promptly the lessons which have been learned to the right people. Engineering groups at Regional HQ and THQ will be keen to give help and information to field staff to resolve problems as they arise. Developments in public call offices will give British Telecom a good opportunity to improve the public image of this important service- at the same time giving staff the chance to work with equipment using present day technology.
TELECOMMUNICATIONS
INSTRUCTION
SELF CONTAINED COIN Telephones Description and Operation
Index
to contents:-
1
Introduction
This instruction describes the Coin Telephone No 22A and outlines its facilities, 100 of these coin telephones have been purchased for field trial in selected Areas. These are pre-production models and some changes will be incorporated if further quantities are purchased.
Further information relating to the
CT 22A is contained in:- 2 General The
Coin Telephone No 22A is a self-contained, mains powered, prepayment unit
intended for use on high revenue sites particularly where there is a large
element of continental and intercontinental traffic. It offers facilities
suitable for IDD, STD and local calls and accepts 2p, 10p and 50p coins. The
instrument incorporates a keypad and credit display. Full operator access is
available. Figures 1 and 2 illustrate the description in the following
paragraphs.
3
Detailed description
3.1
Casework
The
dimensions are:-
The
casework design offers a high degree
of security against unauthorized
entry. The upper, mechanism,
compartment has a door hinged on the
left and secured on the right by a
good quality lock operating a bolt
system. The lower, cash compartment
has a drop door secured by a similar
lock and bolt system.
3.2
The coinbox is secured to a mounting
frame by bolts which are accessible
only from inside the cash
compartment and mechanism
compartment. The mounting frame is
fixed by bolts which can only be
reached when the coinbox has been
dismounted.
3.3
Connections to the box are via a
6-way terminal/contact strip in the
center of the mounting frame. A
6-way contact strip on the back of
the coinbox picks up the connections
automatically when the box is hung
on the mounting frame. The
earth connection is to the mounting
frame and is extended to the box via
the bolts which secure the box to
the frame.
3.4
The handset is supported in the
pendant position on a forked gravity
switch hook on the left of the box.
A standard PO handset No 11 is used
but the plastic cord is replaced by
flexible conductors in a flexible
stainless steel sheath anchored
securely to the handset and gravity
switch assembly.
3.5
The gravity switch hook assembly
carries a follow-on call button on
the front face which in obscured by
the handset when it in on-hook. All
components of the assembly are
readily interchangeable after
removal of a plate on the rear of
the assembly. The whole assembly is
secured to the case by a spigot
which passes through a heavy steel
collar on the inside of the case.
Rotation of the collar clamps the
spigot with a powerful cm action.
Connections from the gravity switch
hook assembly are by means of plug
ended card. 3.6 The mechanism compartment door carries a sloping, protruding console which houses the keypad, credit display and bell and contains three windows for instructional displays, credit display and exchange number label in that order from top to bottom.
3.9
The user instruction displays
consists of an 'INSERT MONEY' legend
in the left hand half and '9990NLY'
legend on the right. They are
invisible until illuminated from the
rear, (Note: on the trial boxes the
999ONLY legend is not used.)
Connections are via plug ended
ribbon cable.
3.10
The bell is a single coil, single
gong unit fixed by two screws and
connected by plug ended cable. A
friction device permits adjustment
of the eccentric gong without
loosening the center fixing screw.
3.11
The exchange number label is a
self-adhesive slip inserted from the
inside of the owe by removal of the
credit display unit (3 screws).
3.12
All display windows are of tough,
laminated glass. Access to all the
sub units in the console requires
removal of the complete coin checker
assembly, ( 4 screws) 3.13 Coin checker assembly. This comprises a back plate, which carries :- (a) the coin entry plate with closure shutter and its operating solenoid (b) the test flap operating solenoid and common slide bar. (c) the accept solenoid and common slide bar. (d) the three coin checkers. (e) the solenoid driver PWB.
Each
coin checker is individually
removable by undoing a knurled
thumbscrew and withdrawing from a
support pin. When in place the coin
checker accept and test flaps are
operated on all three coin checkers
simultaneously by the solenoids and
slide bars.
3.14
Each coin checker is based on a
moulding in a wear resistant, low
friction, plastics material. The
moulding, in cooperation with a
hinged test flap, provides a coin
entry and testing channel which
gives access to either a reject
channel or storage channel in the
lower portion of the moulding.
Rejected coins pass straight through
the reject channel and are returned
to the customer. Accepted coins pass
into the storage channel and are
either cashed under the control of a
cashing electromagnet or refunded on
operation of the refund
electromagnet. each coin checker
carries a PWB containing the control
and drive circuitry for the
electromagnets and the circuitry for
carrying out a materials check on
each coin.
3.15
Connections to all three coin
checkers and to the solenoid driver
PWB is by means of a connection PWB
carrying appropriate connection
sockets and plug ended ribbon cable.
3.16
The microprocessor PWB and Speech
and Interface (S&I) PWB are carried
in a pivoting frame in the main case
of the box. The frame locks in both
closed and open positions and must
be lifted before it can be moved.
The PWB's slide in guides and edge
connection strips engage with socket
connectors on the frame. Each PWB
carries two card ejectors to
facilitate withdrawal of the card
from its connection socket.
Replacement of a board requires only
that the board is slid into its
guides and firmly pressed home in
the connector by pressure on the
ejector. The cards are keyed and
cannot be interchanged. The
microprocessor PWB carries the
processor and associated logic,
accounting and timing components.
The S&I PWB carries the telephone
speech circuit, alarm circuitry,
meter pulse receiver and the
components which enable the
processor to monitor the circuit
conditions which arise during the
operation of the box and to
implement its control signals. 3.17 The Power Supply Unit (PSU) is mounted in the main case below the main PWB's. It is by far the bluest part of the "blue" payphone. Input to the PSU is at 24v ac or do and the box is thus completely safe for users. PSU outputs are:- 24v dc for solenoid operation 15v dc for microprocessor and logic 5v dc for credit display and instruction indicator lamps 5v dc for mains failure refund logic. 34,000 micro farads of smoothing/storage capacitors are sufficient to bridge power input interruptions of up to 1 second duration without impairing the function of the box. In the event of a longer break there is sufficient stored power available to refund unused credit to the user and release the call. Coins in store representing used credit are held in store and not cashed until power is restored.
3.18
Power consumption of the CT 22A
varies from 4.8 w when the box is
quiescent to a peak load of 36 w
during solenoid operation.
3.19
The 24v ac supply to the box is
normally provided by an independent
240/24v step down transformer. 3.20 Tariff setting is determined by a pre-programmed, plug-in unit on the microprocessor PWB. A tariff change entails replacement of the plug-in unit.
3.21
The cash compartment cover carries
the refund cup which is provided
with two hinged flaps. The outer
flap is of clear plastics material
which allows customers to see coins
lying in the bottom of the cup. To
reach the coins the flap has to be
pushed backwards and in this
position the flap closes the
aperture via which coins reach the
cup from the upper compartment. To
provide additional security against
unauthorised access to the mechanism
compartment -a second, stainless
steel, flap normally closes the
aperture from the mechanism
compartment under the tension of a
light spring. The weight of a coin
is sufficient to depress this flap
to allow the coin to drop into the
cup.
3.22
The cash container content meter is
mounted on the right hand side of
the cash compartment cover. This
meter registers the total value of
coins falling into the cash
container. The meter is sealed.
3.23 At the rear of the cash
compartment is a rod protruding
forwards which, when the cash
container is inserted, opens the
container coin entry shutter and
holds it open whilst the cash
container remains in position.
Removal of the cash container
releases the shutter to seal the
container. After this, the container
cannot be re-inserted until it has
been unlocked and the shutter
mechanism has been reset from
within.
3.24 The cash container is of
stainless steel construction and has
a volume of 2.6 litres. It
incorporates a coin level detector
which, when the container is full,
conditions the coinbox control
circuitry so that further coins
inserted are returned to the
customer. In this condition only
non-chargeable calls can be made. 3.25 A cash container presence detector in incorporated in the cash compartment. This also ensures that unless a cash container is in situ only non-chargeable calls can be made. 4 Operation 4.1 The operation of the CT 22A is controlled by a microprocessor. All functions in the box are operated, directly or indirectly, by signals generated by the processor and all functional elements generate signals which are fed to the processor to enable it to monitor their status. The processor responds to signals fed into it in accordance with a predetermined programme which covers all possible conditions and sequences of operation. The 4265 is a general purpose I/O device designed to interface with the MCS-40™" microcomputer family. This device provides four software programmable 4-bit I/O ports which can be configured to allow any one of fourteen unique operating modes for interfacing to data memory or a variety of user peripheral devices.
4289 - Standard
Memory Interface
The 4289 standard memory
interface and I/O interface enables the CPU devices to utilize standard memory
components as program data memory. Notably, PROMs (4702A), RAMs (2102) and ROMs
can be arranged in a memory array to facilitate system development. Programs
generated using the 4289 interface can be committed to MCS-40T ROMs (4308 and
4001) with no change to software. The 4289 also contains a 4 bit bi-directional
I/O port and necessary steering logic to multiplexa host of I/O sources to the
CPU. The Read and Write Program Memory instruction allows the user to store data
and modify program memory. The device directly addresses 4K of program memory.
The address is obtained sequentially during A1-A3 states of an instruction
cycle, The eight bit instruction is presented to the CPU during M1 and M2 states
of the instruction cycle via the four bit data bus. The 4289 stores the SRC
instruction operand as an I/O address and responds to the ROM I/O instructions (WRR
and RDR) by reading or writing data to and from the processor and 4289 I/O bus.
4201A CLOCK GENERATOR
The 4201A is a CMOS integrated
circuit designed to fill the clock requirements of the MCS-40 microcomputer
family. The 4201A contains a crystal controlled oscillator (XTAL external),
clock generation circuitry, and both MOS and TTL level clock driver circuits.
The 4201A also performs the power on reset function required by MCS-40
components and provides the logic necessary to implement the single-step
function of the 4040 central processor unit.
4.2 Automatically connected call. The user lifts the handset, the gravity switch operates and signals the processor which:- Operates the cashing electro magnets on the coin checkers until all coins present in the storage channels have been cashed. Lights the credit display to read 00.00. Flashes the credit display until the minimum call fee has been inserted. Connects the calling loop via the telephone speech circuit to line. 4.2.1 As the user inserts coins they are validated by the coin checkers and either taken into the storage channel(s) or rejected. Each valid coin's value is registered in the processor's memory. When the minimum call fee has been recognised the processor causes the credit display to stop flashing and turns off the 'INSERT MONEY' sign. It also removes the inhibition on the keypad which permits only 3 digit numbers to be keyed. 4.2.2 Provided that the exchange has returned dial tone the user may then key the required number. Each key depression is signalled to the processor which stores them sequentially in the memory. As, soon as any keyed information arrives into the memory the processor then proceeds to transmit it, in the form of standard loop/disconnect impulses, to the exchange. The timing of the pulses in under the control of the processor and a crystal clock which is used as the time base for all functions of the box. 4.2.3 After all keyed-in information has been sent to the exchange call routing and connection is performed by the exchange in the normal manner, ringing tons is fed back to the user. 4.2.4 When the called subscriber answers the Subs Private Metering Relay Set (SPM) in the exchange feeds a meter pulse out to the coinbox in the form of a balanced 50hz signal on both legs of the line, to earth. The Meter pulse receiver in the coinbox recognises this signal and signals the processor which records the event in the memory and starts timing the interval to receipt of the next pulse. The processor also decreases the reading on the credit display by the minimum call fee. Conversation may now proceed. 4.2.6 When the second meter pulse is received the event is recorded and the time interval between it and the first pulse is noted. This interval identifies the charge rate in use on the call which has been made. 4.2.7 The coinbox is connected to ordinary subscribers meter feeds but:- (a) in order to give exact value for money the call timing has to be related to the value of the minimum coin which can be inserted. and (b) a call charge rate rather higher than that appropriate to a ordinary subscriber has to be levied to cover the additional cost of providing and maintaining the call office. Thus, based on the exchange meter pulse rate, the coinbox starts to generate debit pulses timed by its own clock which it uses in place of the meter pulses to control the timing of the call. 4.2.8 Ten seconds before credit is due to expire (as timed by the internal clock, ) the processor injects 5 pips of 400 hz tone into the speech circuit, starts to flash the credit display and lights the 'INSERT MONEY' sign. If money is inserted these signals stop, the value of the money inserted is added to the credit display and the call continues. If money is not inserted the processor disconnects the call as soon as the time paid for has expired. NOTE The foregoing paragraphs 4.2 - 4.2.8 have been set out to illustrate the role played by the processor in controlling the operation of the coinbox. From here on the detail of processor intervention will be omitted and only the effective information described. 4.3
On any call, if the user wishes he may terminate the call by pressing the
follow-on call button. This will cause the exchange connection to be
released but will not initiate the cashing-up procedure. On release of the
button dialling tone will be received and the remaining credit, (provided
that it is above the minimum call fee,) may be used to make further calls. 4.4
When the handset is replaced the call in progress will be terminated and the
cashing-up procedure will take place. The box will automatically cash into
the cash container coins to cover the value of the call which has been made
and will return coins in excess of this value to the user. The box will take
the minimum value from the coins in store which will cover the cost of the
call. This is referred to as 'Best deal accounting'. 4.5
If 1 x 50p coin, 2 x 10p coins and 4x2p coins have been inserted - which
will be shown on the credit display as 00.78p - and the cost of the call
made is 26p, the box will cash the two 10p coins and three 2p coins and will
refund the remainder. If the cost had been 52p the 50pcoin and one 2p will
be taken, and the rest will be refunded. 4.6 If a single 50p coin has been inserted and the cost of the call(s) made amounts to, say 22p, if the handset is replaced at the end of the call the box will be forced to take the 50p coin. However, by terminating the call with the follow-on call button the user will then have the opportunity to insert smaller coins to the value of 22p so that when he replaces the handset the box will cash the 22p and return the 50p coin.
4.7
Incoming calls may be received by the box. When such a call is received an
identity tone consisting of alternate pips of 800 and 1200 hz tone will be
connected to the speech circuit for a period of 10 seconds. This will enable
a distant operator to recognise that the call is to a coinbox and, if a
reverse charge call is required, she will be able to collect money from the
coinbox user taking the call before connecting. 4.8 Outgoing operator controlled calls. 4.8.1 Three digit codes may be keyed without insertion of money. After the 3rd digit has been keyed the credit display stops flashing. 4.8.2 Chargeable calls to 3 digit codes. (100, 102, 103 etc) When such a code is keyed the box will condition itself to refund any coins inserted for a period of 40 seconds after the final digit has been keyed. This is to prevent money being inserted and stared before it can be monitored by an operator. Coinbox identity tone is generated and will remain on for the duration of the call. 4.8.3 When coins are inserted, coin value tones are transmitted to line but are inaudible to the user. The tones are:- 2p One short pip of 400 hz tone. 10p three short pips of 400 hz tone. 50p One long pip of 400 hz tone. The capability exists of transmitting an additional signal of two short pips, digit non chargeable codes. ( 999, 151 etc. These are similar to those to chargeable codes but the identity tone is not generated and the box will refund inserted coins throughout the call. 4.8.5 Chargeable operator controlled calls made as 'follow on' calls after a keyed call has been made, with credit remaining, In
this circumstance the residual credit is 'frozen'. Coins inserted on the
instruction of the operator will be cashed immediately (with coin value tone
transmission,) but the credit stored in the memory will remain unaltered. On
completion of the timed, prepaid operator call the remaining credit may be
used for further auto calls as if there had been no interruption, or, if the
handset is replaced, the box will cash up taking account only of the auto
call charges, 4.9 Coin validation 4.9.1 Maximum diameter and maximum thickness are gauged by the coin entry plate 4.9.2 Minimum diameter, minimum thickness and the material content of coins are checked by the coin checker. For the thickness and diameter check see E5C 3103 for details. 4.9.3 The material check is carried out electronically whilst the coin is momentarily held stationary in the coin runway.
4.9.4 The passage of the coin from the point of entry to the coin checker to
the position in which the material check is carried out is timed precisely.
If this is not completed within a set time, eg because the coin is on a
string, the coin will be rejected and the string (if any) will be cut, If
the time is exceeded due to the presence of foreign material in the runway,
the release of the coin check flap is likely to cause the coin to be
rejected and the foreign material to drop clear.
4.10 Self diagnostics
4.11 Self reporting 4.12 For the purposes of the field trial the fault reporting cable pairs will be terminated on a specially provided equipment located at a suitable central point. An alarm condition will cause a lamp to light - flashing for a cash container alarm, steady for a fault requiring engineering attention. An optional audible alarm will be provided together with a 'receiving attention' facility. Removal of the alarm condition from the fault reporting pair will give a positive indication at the central station. (Note: It is planned that the self routining capability will be considerably enhanced if the CT 22A is purchased in quantity so that faults can be detected in many of the main sub assemblies and a coded signal produced which will indicate which assembly is faulty. The self reporting capability will also be enhance( to transmit the coded fault signal, hopefully over the normal coinbox line.)
Supplier
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Last revised: September 24, 2025FM |
