ANSWERING SET No. 1

Sales Brochure - DLE520.

User Guide
Maintenance Guide Notes
POEEJ Article - 1960

TELECOMMUNICATIONS INSTRUCTION
C MARKETING INSTALLATION
3 Internal
M1001
Issue 2, Aug 73

ANSWERING SET No. 1A
Description and Installation

INTRODUCTION
This Instruction describes the various types of Answering Set No. 1A, which supersede the now obsolescent Answering Set No. 1 (made by Sontronic Ltd). The Old No. 1 used valves and 3000 type relays in it's circuitry. Tape movement was controlled by a microswitch associated with the pinch wheel. When the join in the tape passes the pinch wheel the microswitch operated. The join in the tape is thicker (0.02) than a normal join.

GENERAL
The facilities, connection and operating procedures of the different versions are the same and this instruction will detail the differences in design and construction. The circuits are shown on Diagram SA5202, and Diagram Notes SA5202 explain the circuit operation of the machines.

FACILITIES
The Answering Set No. 1A is a device for use in a subscribers premises for the purpose of answering telephone calls automatically and playing a recorded message to callers. The message is of 20 seconds duration and is played twice to the caller. Recordings, on a loop of magnetic tape, are made and checked by means of the associated telephone. Transmitter current is supplied to the telephone from the answering set when it is switched to the Check and Record positions. The answering set operates from a mains supply of 200-250v ac 50 Hz. It is suitable for use in auto and CB exchange areas on exclusive DEL's, PBX extension, extension plans and HES. The answering set is not suitable for use on shared service lines or in magnet areas.

The answering set is not designed for direct connection to a switchboard e.g. in place of the operators' telephone. It may, exceptionally, be used with a PABX extension arranged for direct night service (see TI C3 F1010 and C3 F1014).

INSTALLATION
The answering set must, generally, be associated with a telephone and cannot as supplied, be used by itself. The telephone should be fitted adjacent to the answering set so the time indicator is visible whilst a recording is being made. Diagram N 4190 shows how the telephone and answering set are connected to the line.

When the answering set is to be associated with an extension plan installation or an HES, an additional telephone must be fitted for the purpose of operating the set.

(a) Mains power Supply
The answering set requires a 200-250V 50 Hz mains supply. A 3 pin socket outlet should be provided by the subscriber within 10ft of the position of the set. The PO will provide the appropriate mains plug.

(b) Connecting the answering set

Remove the case and base (see Constructional Features for appropriate machines). The voltage adjustment panel is reached by removing the Danger label; the connections on this panel are soldered.

Fit the appropriate mains plug.

Connection to DEL or PBX extension Terminate the 6 way answering set cord on a Block Terminal No. 35A. Change the telephone line cord to a Cord Instrument No. 6/61 AT..... 3000 mm and connect as shown in N4190.

Connection to extension plan or HES Change the answering set cord to a Cord Instrument No. 9/21 AD GREY 3000 mm and connect as shown in N4190.

PRECAUTIONS DURING INSTALLATION
The mains plug must be withdrawn before any work is done on the machine. Permanent magnets or magnetised tools must not be brought near the record/replay head of the machine. The output of the set will be affected if the head becomes magnetised.

Care should be taken to ensure that the machine is not installed in the proximity of strong a.c. fields and that the leads to the answering set are not routed near machinery likely to generate interference fields.

After installation all the spindles and wheels in the tape drive system where friction drive is used should be wiped with a clean dry cloth to remove dust and grease which could cause slipping.

Before the cover is finally replaced ensure that the pointer moves freely over the whole length of the time indicator scale.

OPERATING THE SET
A copy of the operating instructions should be handed to the subscriber at the time of installation but it is desirable that the fitter should ensure that the subscriber is familiar with the facilities provided and the method of using the set.

The Answer Set No. 1A/2 uses a lamp instead of the indicator to show the motor is running

The following notes summarise the operating instructions:-

(a) Recording
Switch the control knob to Record. Lift the handset, press the Start button firmly and then release it. As soon as the indicator pointer appears, speak normally into the mouthpiece and continue until the pointer disappears. It is desirable to avoid gaps during or at the end of the message.

(b) Checking
When the motor indicator stops turning switch to Check, press the Start button, and listen to the message on the handset. The message will only be played once.
(An incoming ring during either of the above operations will ring the telephone bell and the call can be answered by turning the switch to Off and using the telephone normally.)

(c) Answering
Switch to On and ensure the mains supply is connected. An incoming call will ring the telephone bell for 5-10 seconds before the set answers automatically. During this period the call can be intercepted by the telephone by turning the switch to Off and using the telephone in the normal way. If a call has been intercepted in this manner the set must be restored to its starting condition by switching it to Check and pressing the Start button.

If it is required to use the telephone normally switch the control knob to Off.
When the answering set is associated with an extension plan or HES the operation differs as follows:-

The telephone associated with the answering set may be used for intercepting calls to the answering set only when the switch is in the On position. In all other switch positions the exchange line is not connected to the associated telephone but to the extension plan or HES. When the switch is in the On position the extension plan is disconnected.

ANSWERING SET No. 1A/1
The Answering Set No. 1A/1 is manufactured by Sontronic Ltd and with the exception of the connections differs completely from other versions of the answering set. The machine is fully transistorised and the ringing delay and tape control are achieved by electronic circuitry and photo-conductor and lamp.

Details of the constructional features peculiar to this machine are given in the following paragraphs.

(a) Removal of case

(i) Remove knob of 4-position switch using Wrench, Hexagonal, No. 1 to release the socket-head grub screw. A wrench can be found set into the base and held by one of the 4 large screws.

(ii) Remove the screws at each corner of the Perspex panel. This panel and the main case may now be removed.

(iii) remove the base which is secured by 4 large screws; the 15-way terminal strip for connecting the set is then exposed.

(b) Chassis assembly
Removal of the front plate and case will reveal the top face of the chassis. Mounted on the top face of the chassis are the tape tray, tape drive system, mains-on lamp, control switch, start button, line transformer and recording time indicator. On the underside of the chassis are mounted the mains connection blocks and fuse, mains transformer, tape drive motor, and the wafer assembly of the control switch. The chassis is mounted on 2 end brackets to which the moulded base is secured.

(c) The printed wiring board
This is secured to the vertical members of the 2 end brackets by 4 fixing nuts. The printed wiring side of the board is insulated by a sheet of impregnated paper covering the whole of the rear face. All circuit components are mounted on the inside face of the board, including relay A which is a PO type 25 relay mounted on a stand-off bracket and wired into the printed circuit. The ringing detector, consisting of lamp and photo-conductor, is mounted under a cylindrical cover retained by a helical spring. To obtain access to the ringing detector it is necessary to release the retaining spring and withdraw the cover. Adjustment of the ringing delay period is provided by potentiometer VR1 located close to the ringing detector. The terminal. strip for cord termination and strapping is mounted on the printed wiring board.

(d) Tape drive and control
All moving parts associated with the tape driving mechanism and the multiple-wager 4-position control switch, are fitted to the sloping member of the chassis, either on top or beneath it. Tape control is achieved by a photo-conductor lamp and a small hole in the tape. The photo conductor is mounted in a masking assembly on the tape tray wall through which a hole is drilled to allow light from the lamp to impinge on it. The lamp is mounted in a plastic holder and protrudes through the base of the tape tray opposite the photoconductor. The plastic holder slides on a lug secured to the underside of the tape tray so that the lamp position can be adjusted with respect to the tape hole and photo-conductor. A grub screw is provided in the plastic lamp holder to ensure that lamp position adjustment is maintained. The spindle of the tape-drive motor extends through the chassis. The motor is supplied with 48V a.c. from the mains transformer whatever the supply voltage. The spring loaded idler-wheel transmits the drive to the rim of the flywheel. The extended spindle of the flywheel imparts driving force to the tape which is pressed against it by the rubber pinch-wheel. The pinch-wheel is mounted at one end of the pivoted lever; pressure between the pinch-wheel and the driving spindle is maintained by a spring which exerts a pull of 3lb. on the lever. The top of the rubber pinch-wheel has a moulded pattern which is visible through the window in the case.

When the flywheel is being driven by the motor, the tape is given a linear velocity of approximately 1.9 in/sec. The tape is pulled out of the storage tray at the upper left-hand corner and passes the erasing head and the record/replay head before reaching the pinch assembly. After passing through the pinch assembly the tape is wiped by an earthed strip to remove electrostatic charges which might cause the convolutions of tape to stick to each other in the storage tray. Under the influence of its forward movement, the tape packs itself into the tray; the lid of the tray, which also carries the scale of the time indicator, must not be removed while the tape is in motion or the tape will spill out and may break or kink.

While the tape is in motion, pressure pads keep it in intimate contact with the erase and record/replay heads, but when the control switch is in the Off position a cam on the switch shaft causes the lever to lift the pinch-wheel and the pressure pads away from the tape.

The flywheel is fitted with a concentric plastic disk in which is cut a spiral groove from the centre to the edge. A nylon stylus tracks across the disk during the recording and checking of a message. The stylus is attached to a cranked and pivoted arm having, at its free end, a pointer which traverses the scale in the centre of the control panel. Operation of the Start button lifts the stylus from the rim of the disk and allows it to fall under gravity to the start of the spiral; at the same time the pointer moves to the Begin Recording position on the scale.

(e) The recording tape
The tape loop is made up from standard 0.25 in wide recording tape 38.5 in long with the ends joined.

A small hole is punched in the tape, off-centre, near the joint, so that it passes between the photo-conductor and lamp.

The tape should not be handled otherwise the performance of the set will be impaired, but if for any reason it becomes necessary to replace the tape in the storage tray the following procedure is recommended.

Turn control switch to Off.

Remove lid of tape tray.

Remove the existing tape.

Feed the tape past the erase and record/replay heads and through the pinch assembly. The matt side of the tape should be against the heads and the small hole is near the lower edge. Feed the tape past the heads and through the pinch wheel until the hole has emerged from the pinch-wheel assembly.

Pass both parts of the tape through the slot in the lower right-hand corner of the tape box. The tape must be free of twists and kinks and it is better to have it hanging free, e.g. over the edge of a table. The tape may be pulled very gently to straighten it.

Replace lid of tape tray.

Turn switch to Check and press Start button. After the tape has been drawn into the tray, the tape drive will be disconnected. A new recording must be made after replacing the tape even if the tape has not been renewed.

(f) Spring adjustments
Screw adjustment is provided for the tensioning springs of the pinch wheel, idler wheel and pressure pads.

ANSWERING SET No. 1A/2
The Answering Set No. 1A/2 is manufactured by Ansafone Ltd and with the exception of the connection differs completely from other versions of the answering set. The machine is fully transistorised and the ringing delay and tape control are achieved by electronic circuitry and photo-cell and lamp. Details of the constructional features peculiar to this machine are given in the following paragraphs.

(a) Chassis Assembly
The case can be removed by the same procedure as for the Answering Set No. 1A/1 except a screw driver is used to loosen the switch knob instead of an Allen key. Removal of the front plate and case will reveal the top face of the chassis. The tape runs round a series of pulleys, one of which is fixed in a slot to provide an adjustment. The tape is tensioned by a spring on the right-hand side of the chassis. The tape drive system, machine on lamp, machine-in-use lamp, start button, the set-level control and the recording time indicator are mounted on the top of the chassis. To gain access below the chassis 4 screws in the corners of the chassis should be removed. The chassis may then be hooked under the front corners of side brackets which will retain the chassis horizontally. The 2 end brackets are mounted on the base, the left-hand bracket has the control switch and relays fitted to it, and the right-hand bracket has, the mains transformer and fuse mounting fitted to it.

(b) Printed wiring board
The printed wiring board is retained at the base between 2 rubber bushes and the side brackets, and at the top by the lip on the chassis. A plastic sleeve is fitted on the top edge of the board to prevent damage when the chassis is replaced.

(c) Tape drive and control
The tape-drive motor, which is driven from a 40V tapping of the mains transformer, is connected to the flywheel by a rubber drive belt. The extended spindle of the flywheel forms the capstan spindle which imparts the driving force to the tape when it is pressed against it by the pinch wheel. The spindle of the pinch wheel drives the indicator wheel which in turn drives the tape indicator. Tape control is achieved by a photo-conductor, lamp and a small window in the tape. The photo-conductor is mounted in a masking assembly under the tape lid cover which has a hole drilled in it to allow light from the lamp to impinge on it. The lamp is mounted in a metal holder which is fitted in a rubber grommet in the chassis.

(d) Spring adjustments
The pressure adjustment of the pinch wheel can be adjusted by loosening the screw at the back of the pinch solenoid and sliding the pinch solenoid backwards or forwards as required. Care should be taken to ensure that the solenoid and the spring attaching it to the pinch wheel bracket are in a direct line.

(e) Recording tape
This is identical to that used on the Answering Set No. 1A/1 except a small window is provided near the joint so that it passes between the photo conductor and the lamp. When replacing the tape, all that is required is for the tape to be put in place and tensioned. The adjustable pulley wheel will account for any differences in tape length. The pulley is held by a screw which is accessible after removing the front deck plate of the machine.

Introduced in 1958

An extract from
THE POST OFFICE ELECTRICAL ENGINEERS' JOURNAL
Volume 53, Part 1, April 1960

An Answering Set for Telephone Subscribers
Answering set No. 1

Design requirements are suggested for a device which will answer a telephone call and give a recorded message when the called subscriber is absent. The way in which these requirements are met by the Post Office Answering Set No. 1 is described.

INTRODUCTION
For many years it has been possible for subscribers connected to certain exchanges to arrange for incoming calls to be intercepted at a manual board and for callers to be referred to an alternative number. This service is particularly valuable to subscribers such as doctors, who can expect to receive urgent telephone calls at any time and who are thus relieved of the necessity of ensuring that someone is always available to answer them.

Unfortunately, this transfer-of-calls service cannot be made available to all subscribers who might wish to use it, and there is a need for an automatic answering device which can be associated with the telephone installation whenever it is not convenient for calls to be answered personally.

GENERAL DESIGN CONSIDERATIONS
It was considered that an answering machine for subscribers� use should provide the following facilities:-

The user should be able to record the message he wishes the caller to hear, and change it as required.
The subscriber.s telephone should be used to record the messages, and the recording process should be no more difficult than making a telephone call.
The user should be able to check the recording he has made by listening to it in the telephone receiver.
The message capacity of the machine must be adequate, but not greater than can conveniently be used fully. To help in this respect, there should be an indicator showing the time available throughout the recording process.
A caller should be able to hear the whole message at least once, even if part of its transmission is interrupted
by pay tone from a pay-on-answer coin box.
Connexion of the machine must not interfere with normal use of the subscriber's installation, and all incoming calls should ring a telephone bell.

The machine described in this article is not required to record the caller's message; other approved machines are already available which will do this.

ANSWERING SET No. 1

Physical Features
An answering device, developed commercially to meet a Post Office performance specification, has been adopted and coded as "Answering Set No. 1". It is an a.c. mains-operated machine using standard tape-recording techniques and used with a Telephone No. 706.

The moulded case of the answering set, which follows the general configuration of the Telephone No. 706, is approximately 12in. wide, 6in. high and 9in. deep; it is two-tone grey in colour.

ANSWERING SET No. 1 WITH TELEPHONE No. 706

Only two controls are needed to operate the set; these are a function-selector switch having the four positions �Off�, �On�, �Check� and �Record�, and a press button which starts the machine when a recording is to be made or checked. Three indicators are provided. One of the two small circular windows shows a pilot light when the mains supply is connected, the other shows a moving pattern when the tape driving system is in motion and so acts as a warning against switching the set to a new function before the previous one is completed. The third indicator is the central rectangular window, showing an edge-lit scale marked �Begin Recording� and �Finish Recording�; a pointer moves between these marks during the recording process.

The machine has wedge-shaped chassis and removal of the cover exposes the tray in which the tape is stored. The sloping panel carries most of the components for the control circuit, and the vertical rear member carries the electronic circuits. A conventional driving system is used for the tape, giving a linear speed of If inches per second. The loop of tape is slightly longer than is necessary for a 20-second message and the excess portion is thickened so that it displaces the tape pinch-wheel at the end of each cycle of operation. The pinch-wheel is mounted at one end of a pivoted lever, so that a small movement of the wheel is mechanically magnified and operates two microswitches held in contact with the other end of the lever. The pinch-wheel also carries a pattern which can be seen through one of the windows in the control panel.

The flywheel of the tape driving system carries a concentric plastic disk in which is moulded a spiral groove running from the centre to the rim. A nylon stylus tracks this groove and, by a cranked lever system, moves the pointer linearly over the time-indicator scale.

To prevent electrostatic attraction between the convolutions of tape in the storage tray, the tape is wiped immediately after passing the pinch-wheel by a metal strip solidly bonded to the chassis.

The set is connected to the associated telephone and exchange line by a 6-way cord terminated on a strip, which is exposed when the base of the set is removed.

Electrical Features
Electrically, the set is in three parts:-

The answering circuit , which includes the function-selector switch and control relays.
A record/replay amplifier , together with the h.f. bias oscillator and the erase and record/replay heads.
A power unit , which supplies h.t. and l.t. to the record/replay amplifier, smoothed d.c. of 50-60mA for the telephone transmitter and partially smoothed d.c. for relay operation.

Facilities
The Answering Set No. 1 can be associated with most of the telephone instruments used by the British Post Office and can be directly connected to any type of exchange service line except C.B.S.1 and shared-service lines.

Incoming calls are answered about 7 seconds after the receipt of ringing current; it is undesirable for the machine to answer too quickly. Calls are answered by the connexion of a transformer winding having a resistance of 120 ohms and presenting an impedance of about 600 ohms to the exchange line. Transmission of the recorded message begins immediately after answering, and a 20-second recording is played twice. If the recording capacity has been fully used, the second transmission begins within 2 seconds of the end of the first. After the repetition, the machine disconnects itself from line and is immediately ready to answer the next call.

The message is recorded by speaking normally into the handset, and it is desirable to use the whole of the recording capacity by talking until the time indicator disappears from view. The recorded message can then be played back into the telephone receiver.

When automatic answering of calls is not required, the set can be disconnected by switching to "Off". In all positions of the selector switch, it is arranged that a telephone bell is included in the line circuit.

Circuit Description
Below is a simplified diagram of the circuit of the Answering Set No. 1. The set is shown associated with a Telephone No. 706.

For automatic answering, the multiple-wafer selector switch is turned to "On". This connects mains to the set, via switch S2, and SI connects relay A in parallel with the windings of the telephone bell. A small proportion of ringing current is rectified to operate relay A, which locks over its own contact via a microswitch, MSI. Contact A2 applies 6-3 volts a.c. to a thermal relay, TR, which operates in 5-7 seconds so providing the required pre-answering delay. The thermal relay contact operates relay B, which in turn operates relay C, so starting the tape drive motor. B3 and B4 connect the 120-ohm winding of the transformer to line to give the answering condition; B2 provides a holding circuit for B via the second microswitch, MS2. The tape is now in motion past the replay head, and the recorded message is transmitted.

When the tape loop completes its first cycle and the message has been transmitted once, the thickened portion of the loop causes both microswitches to open momentarily. The locking circuits of relays A and B are broken, but the latter relay remains operated because the thermal relay contact TR1 is still closed. As relays B and C remain operated, the tape motor continues to run until the micro-switches are again opened by the thickened tape at the end of the second message transmission. Relay B now releases because TR1 has opened and there is no alternative holding path. The output transformer is disconnected from line by B3 and B4. When, in turn, relay C releases, the motor stops and the set is -ready to receive the next incoming call.

While the set is switched to �On�, normal telephone service is available from the associated instrument.

SIMPLIFIED CIRCUIT OF ANSWERING SET No. 1 ASSOCIATED WITH TELEPHONE No. 706

Making a Recording
The selector switch is turned to the "Record" position and connects the whole of the telephone transmission circuit to the input of the amplifier. It also switches smoothed d.c. to the transmitter. The user gets normal telephone speech conditions, including some side-tone, while recording and he unconsciously adjusts his voice to normal level without the aid of a volume indicator. The ringing circuit is switched via a 2uF capacitor in the set in order that ringing current from an incoming call can be applied to the telephone bell even if the switch is left in the "Record" position. While a recording is being made there is no connexion between the speech circuit and the exchange pair. In the amplifier, the selector switch applies h.t. to the bias oscillator, connects the input transformer to a power amplifier and connects the amplifier output, together with bias current, to the record/replay head of the tape system. At the same time, bias current is applied to the erase head to remove the previous recording.

The recording process commences when the "Start" button is pressed. This action sets the indicator pointer at the beginning of the time scale, and also operates relay B mechanically. As before, the tape drive motor is switched on, cycling the tape once until the microswitches are opened; when this occurs, relay B releases and relay C cuts off the motor.

Checking the Recording
In turning the selector switch from "Record" to "Check", the only circuit changes are in the amplifier unit where the record/replay head is now connected to the input of a high-gain voltage amplifier, and h.t. is disconnected from the bias oscillator. Operation of the "Start" button, as before, causes the tape to make one cycle during which the recording is heard in the telephone receiver but, because an attenuator is added to the amplifier output in this switch position, the recording is 3db or 4db below the level which is available for transmission to line. By this means the user is able to hear the message at about the same volume as a local caller will hear it, and can satisfy himself as to its volume and clarity.

When standard direct-exchange-line service is required, the function switch is turned to �Off�, disconnecting the mains supply, providing through circuits from the exchange pair and electrically dissociating the set from the telephone circuit.

Use of the Answering Set with Multi-Instrument Installations
To avoid complications in the wiring of extension plan and similar systems, straps are provided in the set so that the exchange line can be intercepted when the function switch is at "On", while in all other switch positions the exchange pair is routed straight through the set. In these circumstances, a separate telephone instrument is provided for recording and checking.

Characteristics of the Record/Replay Amplifier
The recording amplifier can accept peak input signals of about 2 volts without distortion, i.e. it can accept the maximum speech voltage likely to be developed in the transmission circuit of a modern telephone; an equalizing network is included to reduce over-emphasis of sibilants.

The replay amplifier contains a compensating network giving a generally rising gain/frequency characteristic which tends to offset loss of higher speech frequencies due to the comparatively low tape speed. The overall effect gives a substantially smooth frequency response over the range 600-2,200c/s, falling by about 8db at the extremities of the speech range of 300-3,400c/s.

The speech voltage output to line closely follows the input level from the transmission circuit of the recording telephone, the variation being of the order of 2db. The caller thus hears the recorded message at about the same strength as he would hear the called subscriber if the call were answered personally.

Power Consumption
The power consumption of the answering set has been kept low - a desirable feature since the set may be connected to answer calls over a long period and since the subscriber provides the power. The consumption is approximately 15 watts in the standby condition and reaches a maximum of 36 watts when a recording is being made.

CONCLUSION
The Answering Set No. 1 caters for those subscribers who require a simply operated device which, in their absence, will give callers a message saying where or when they can be located.

ACKNOWLEDGEMENT
The author wishes to thank Sontronic, Ltd., of Edgware for their co-operation in the development of the answering set.