TELEPHONE RP3771


P.O. ENGINEERING DEPT. ENGINEERING INSTRUCTIONS
TRANSMISSION
TELEPHONE
R 1604
Issue l, 19.11.58

MULTIPLE-ACCESS TELEPHONE EQUIPMENT (M.A.T.E.)
Description

1. General
This Instruction describes the Multiple-access Telephone Equipment (M.A.T.E.) which is being provided for the termination of speaker circuits and exchange lines in the larger repeater stations.

2. Facilities
Special speaker switchboards or telephones to which all speaker circuits and exchange lines are connected are provided at selected points in the station. These provide facilities for calls to be originated or received on any circuit (or exchange line) at any of the selected points without the intervention of an operator. Microphones, connected to a loudspeaker system, can be provided at each point so that any officer may be called to speak on the calling circuit.

3. Incoming calls operate a relay-set which lights a calling lamp on each switchboard and connects a tone over the loudspeaker system (or operates a station bell at those stations where a loudspeaker system is not justified). In stations where specific exchange lines or speaker circuits are allotted to different functional groups, e.g. audio, carrier, or coaxial maintenance or works orders, and where the lines are shared between different floors, distinctive tones may be used to indicate the group required. 300, 500 or 800 c/s are normally provided but if these do not give sufficiently distinct signals other frequencies may be used.

4. Outgoing calls can be originated from any switchboard or telephone, all of which have facilities for loop calling, loop dialling, 17 c/s ringing, balanced battery or v.f. tone signalling. Busy lamps associated with each circuit are provided on all switchboards and telephones to indicate engaged lines.

5. Equipment
The equipment necessary for a complete installation comprises the following :-
Equipment, Speaker, RP 4633
Panels, Speaker, RP 4634
Switchboards RP 3751, 18/18 or 36/36
Telephones RP 3771
Microphones and loudspeakers.

(NOTE: At certain early installations an Equipment, Control, was provided in place of the Equipment, Speaker).

The drawings and diagrams for these equipments are given in Table 1.

6. Equipment, Speaker, RP 4633
The Equipment, Speaker, RP 4633 comprises a 9 ft. 0 in. or 10 ft. 6 in. Rack, Apparatus, No. 42.... which accommodates the calling relay-sets (Panel, Speaker, RP 4634), Oscillators No. 13.... (for calling signals) and loudspeaker-amplifiers. 

7. The Panels, Speaker, RP 4634 are fitted on the front of the rack which, when fully equipped, will accommodate 18 panels (36 circuits). The equip­ment will normally be wired for either 9 or 18 panels depending on the size of the station and the number of panels actually fitted will depend on the number of speaker circuits provided.

8. On the rear of the equipment accommodation is provided for three Oscillators No. 13...., two loudspeaker-amplifiers, a tone distribution panel and a fuse-mounting and ringing resistance lamp panel for providing battery and 17 c/s ringing distribution to the speaker switchboards.

9. Panel, Speaker, RP 4634
Each Panel, Speaker, RP 4634 accommodates two speaker calling circuits which will operate to 17 c/s or balanced battery signals by appropriate strappings on the panel connexion strip.

10. The interconnexion of the Panel, Speaker, RP 4634 and Switchboard RP 3751 and Telephone RP 3771 is described below.
Relay L operates to the incoming 17 c/s or balanced battery, Ll operates relay LL which locks via LLI and B2; LL2, 3 and 4 (LL2 only shown) extend 1 30V to light calling lamps on switchboards and LL5 and 6 extend tone to the loudspeaker system. The call is answered by operating the appropriate speak key on any switchboard or selecting the calling line and lifting the handset of a Telephone RP 3771 (see par. 14). In each case an earth condition is returned to the speaker panel to operate relay B. Bl disconnects relay L, B2 releases the locking circuit of relay LL and B3, 4 and 5 (B3 only shown) extend l3OV to light the appro­priate engaged lamp on all switchboards and any telephones switched to that line. Relay LL releases and LL2, 3 and 4 break to extinguish the calling lamps. On completion of the call restoration of the switchboard speak key or replacement of the telephone handset disconnects the earth to release relay B and the circuit is restored to normal.

TABLE 1

Equipment Schematic Wiring Assembly Cross-connexion
Equipment, Speaker, RP 4633 Panel, Speaker, RP 4634 Switchboard RP 3751 Telephone RP 3771 Equipment, Control RP 4633 RP 4634 RP 3751 RP 3771 RP 3751 RPW 4633
RPW 4634
RPW 3751
RPW 3771
RPW 3751
RPA 4634 Drg. 66937 Drg. 66638 Drg. 66627 RPA 3751

RPX 3751

11. Switchboard RP3751
There are two sizes of switchboard available which accommodate either 18 or 36 lines. Both are built into metal cabinets suitable for rack, wall or table mounting and their overall dimensions are 17 in. x 8.75 in. x 4.75 in. and 17 in. x 12.25 in. x 4.75 in. The picture to the right shows a 40-line switchboard provided on an early installation; the present 36-line switchboard is identical except in the number of lines it accommodates.

12. Calling and engaged lamps and a speaking and ringing key are associated with each line. The ringing key is a locking type to simplify the provision of holding facilities on exchange lines. The lamps used are miniature neons with a current consumption of approximately 1 mA and are operated from the l30V supply. The illumination from the lamps is not so great as with Lamps No. 2.... but it is found to be adequate bearing in mind that an audible signal is also given. A switchboard should not however be placed in such a position that natural lighting will make it difficult to identify a glowing lamp. 

13. Additional non-locking keys provide for the connexion of a dial, 17 c/s ringing, 300, 500 or 800 c/s tones or balanced battery for outgoing calls. The telephone circuit is terminated on a Telephone No. 184 via a Jack No. 19 and wiring is provided to enable the circuit to be extended if required to an additional Jack No. 19. On an auxiliary test rack (A.T.R.) or other position giving speaking facilities at the equipment racks. Also built into the switch­board is a moving-coil microphone which is con­nected via a key to the input of the loudspeaker-amplifier.
 
14. Telephone RP 3771
The Telephone RP3771, which is shown to the right, provides for the termination of 10 lines with a single calling lamp and an engaged lamp and gives the same signalling conditions for outgoing calls as the Switchboard RP 3751. It consists basically of a local-battery telephone modified by the addition of a special base unit accommodating two rotary switches, a ringing key and the calling and engaged lamps.

The 10 lines terminate on one switch so that any line may be connected to the telephone. The other switch selects the signalling condition to be applied to the ringing key for outgoing calls.

On receipt of an incoming call an audible signal is received over the loudspeakers (or the station bell). It is then necessary to search for the calling line by rotating the first rotary switch until the call lamp glows. Lifting the handset then extends an earth to the Panel, Speaker, RP 4634 to release the calling condition and light the busy lamps.

15. For outgoing calls the first rotary switch is switched to the required line; should this be engaged the engaged lamp will glow. If the circuit is dis­engaged the second rotary switch is set to the appropriate signalling condition and the ringing key operated.

16. A microphone for use with the station loud­speaker system is not built into the Telephone RP 3771 but if required a separate desk microphone can be provided.

17. Loudspeaker arrangements
The loudspeaker-amplifiers, microphones and loudspeakers are proprietary items manufactured by Messrs. Pamphonic Reproducers Ltd. The manufacturers’ codes for these items are given in Table 2.

18. These items will only be required in large stations or stations having unusual layouts or occupying more than one floor. Where loudspeaker facilities are required two amplifiers should be fitted, one worker and one reserve, the inputs and outputs being wired via a U-link change-over panel. Each amplifier has two inputs, MIC and GRAM. The microphones are connected to the MIC input and the GRAM is used for the calling signal tones. This arrangement allows separate adjustments of the amplifier to cater for different input levels from the microphones and signalling tones.

19. Power supplies
The power supplies required by the equipment are given in Table 3.

In a station where there are no d.c. supplies a Panel, Power, No. 25A (24V d.c.) should be provided for relay operation and transmitter battery supplies and a Power Unit RP 3046 (6V a.c. and l30V d.c.) for the Oscillators No. 13 and the calling and engaged lamps.

20. Incoming calls other than 17 c/s or d.c.
As stated in par. 9, the speaker panel will operate to 17 c/s or d.c. (battery) signals. Various other conditions are met in practice and the arrangements for other signalling conditions are as follows:-

(a) Loop calling
When an extension telephone is to be connected to the speaker system it should be connected via Unit, Signalling, No. 7 as shown in Dgm. RP/RPW 3664.

(b) Tone calling
When a speaker circuit employs v.f. tone signalling, a Unit, Signalling, No. 3 or No. 18 (for 500 c/s) or a Unit, Signalling, No. 11 (for 300 or 800 c/s) should be provided.

TABLE 2

Item Manufacturers’ code Remarks
Loudspeaker-amplifier No. 600 W/RM Type 600 V was provided on early installations
Microphone .... No. 948 P Built into the switchboard
Microphone .... No. 765 S For use with telephones and requires a mounting to be constructed locally
Loudspeaker .... No. 776 A  Rack fitting or for suspension from overhead ironwork
Loudspeaker .... No. 775 C Wall fitting

TABLE 3 

Supply Use
24V or 50 Vd.c. Relays on Equipment, Speaker, RP 4633 Transmitter battery on switchboard and telephones
130V d.c. .... .... Calling and engaged lamps on switchboards Oscillator anodes
230V a.c .... Loudspeaker-amplifier

21. Omnibus speaker circuits
The multiple access telephone equipment may be connected to a 4-wire omnibus speaker circuit either as a terminal or an intermediate station. On circuits employing d.c. code signalling, d.c. code 1 can be accepted by a terminal station; intermediate stations cannot receive d.c. code signals but the circuit provides for their repetition. The circuit arrangement and operation are given in Dgm. RP 4809 and Dgm. Notes RP 4809 for terminal stations and in Dgms. RP 4810 and RPX 4810 and Dgm. Notes RP 4810 for intermediate stations.

 

 
 
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Last revised: December 18, 2010

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