|P.O. ENGINEERING DEPT. ENGINEERING INSTRUCTIONS
Issue l, 19.11.58
MULTIPLE-ACCESS TELEPHONE EQUIPMENT (M.A.T.E.)
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.
(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.
Switchboard RP3751 with Telephone RP3771
6. Equipment, Speaker, RP 4633
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
10. The interconnexion of the Panel, Speaker, RP 4634 and Switchboard RP 3751 and
Telephone RP 3771 is described below.
11. Switchboard RP3751
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.
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
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
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.
(a) Loop calling
(b) Tone calling
21. Omnibus speaker circuits
Last revised: June 30, 2018