Patent GB-417797-A (GB)
Title: Improvements in, or relating to police call systems
IPC: H04M11/04
Filed: 1933-04-18
Abstract: 417,797. Police alarm systems; road signals for controlling traffic. SPEIGHT, A., 10, Rowanlee Drive, Giffnock, Renfrewshire. April 18, 1933, No. 11281. [Classes 40 (i) and 118 (ii).] In a police alarm system, the two-wire line circuit terminates at the central station in a single line relay of the two-step type and a small current normally flows over the line partially to operate the relay which has two windings connected between the lines and a centre-pointearthed battery so as to respond to alarm or call signals and also to all fault conditions. The system described with reference to Figs. 1 to 7, comprises an alarm originating circuit, Fig. 1 (situated within a building), a local alarm indicating circuit, Fig. 2 (exterior to the building), and a neighbouring traffic control circuit, Fig. 3, provided with alarm signals. These three circuits are associated with control relays certain of which are normally partially operated, an alarm transmitter and a telephone set, Fig. 4, located at a convenient point and connected over the line circuit 23, 24 to receiving arrangements, Fig. 5, at a central station also provided with telephone circuits, Fig. 7, connected over terminals 25-27 to the receiver, Fig. 5. Constructions of alarm transmitter, receiving selector, and traffic signal-post are also described. Alarm signalling from out-station. One of the keys KA, KB, KC, Fig. 1, is thrown to short circuit resistance XA whereupon RC operates fully and the various lamps in the alarm circuit light up. Slow operating relay RE pulls up and operates magnet MA to release the alarm transmitter which closes off-normal contacts ma1 to complete a low resistance loop and sends out the alarm signal over contacts ma2. Relay RC also lights the exterior lamps LD, LE, Fig. 2, and reverses the battery on the line leading to the traffic signals, Fig. 3, so that RB pulls up followed by RA which lights the all-traffic-stop lamp LF, the alarm identifying lamp LG, permanently lights the red traffic lamp LH and disconnects the green and amber lamps LJ, LK. The audible traffic alarm HA is also operated. After the alarm signal has been transmitted, the sender momentarily closes ma3 to operate RG which releases RE followed by magnet MA so that the sender is held when it has reached normal. At the central station, Figs. 5 and 6, the two-step relay RJ operates fully on completion of the low resistance loop at the outstation, slow release relay RM pulls up to operate magnet MB controlling the locking pawl of the receiver and impulses are repeated by RJ to the receiver stepping magnet MC. When the signal ceases, RJ falls back and spring set mc1 operated by the receiver holds MB, and therefore the receiver operated, energizes alarm lamp LR and relay RP, and operates RK. The alarm relay RP lights lamp LS and operates the audible alarm HC. Relay RK disconnects the fault relay RL, reverses the current flow over the line and at the same time increases current flow, by cutting out resistances XE, XF, but not sufficiently to cause RJ to pull up fully. At the outstation, battery reversal operates RH which opens its own circuit at the mercury switch rh1 so that RH operates intermittently to flash the lamps in the interior and exterior circuits, Figs. 1 and 2, and lamp LG at the traffic control point, Fig. 4, while the breaks of the line circuit also cause the full release of RJ which, at rj1x, flashes supervisory lamp LO. When the alarm has received attention at the central station, key KF is thrown to release the receiver and restore the central station circuits to normal. The lamps at the outstations glow steadily until the alarm key KA-KC, Fig. 1, is restored. The operator may stop the alarm signal HC, before the alarm circuits are cleared down, by throwing up the linked switches KG-KI, Fig. 6. When the circuits are cleared, RP falls back, lamp LT glows and an audible signal BA is given to indicate that the switches KG-KI should be restored Telephony. A call from the outstation is made by sending a digit from a dial or other transmitter (off-normal and impulse springs da, db, Fig. 4) so that the central station receiver is set to operate the spring set mc2, with results similar to the alarm signal except that a different alarm circuit LQ, RO is completed. Relays RH at the outstation and RJ at the central station operate intermittently as before. When the receiver at the outstation is lifted, relay RH is mechanically locked operated by a pivoted gravity catch t, Fig. 9, released by the switch hook SH, and the speaking circuits are completed at switch-hook contacts sh1, sh2, lamp LM being lit at sh3. The operator at central throws KD to connect up the telephone equipment, Fig. 7, battery being fed to the out-station and to operator's set over relays RQ, RR. If the key KD is left thrown or the operator's receiver left off the switchhook after a conversation, lamps LU, LV light up respectively and RT pulls up to actuate an alarm BB. The operator may call the outstation by throwing key KE whereupon RK lights lamp LO and sends the battery reversal signal. At the distant end, RH operates intermittently over its mercury switch contacts rh1 and actuates the call signal HB while the intermittent full release of RJ at the central station flashes LO to give supervision. When the outstation replies, RJ operates fully over the low resistance loop and LO glows steadily. The operator then throws KD to complete the speaking connection. Fault alarms. The resistances in the alarm originating circuit, Fig. 1, local alarm circuit, Fig. 2, and the line circuit to the traffic point, Fig. 3, are such that, normally, relays RC, RD, RF are partially operated and have their x contacts open. A disconnection in either of these circuits releases the relays to place full ground on one of the main signalling wires in Fig. 4. A short-circuit or ground on the local alarm circuit or the line to the traffic point fully operates RD or RF with the same results. The line relay RJ, Fig. 5, of the main signalling circuit is also normally partially operated with its x contact open. In case of a disconnection, or battery failure in this circuit, RJ relapses and after a predetermined time a thermal or delayed action relay RL completes a circuit for lamp LP and relay RN which brings in an alarm (not shown). A short circuit or ground on the main circuit, including the ground signals due to faults on the above mentioned subsidiary circuits, operates RJ fully also to energize the thermal relay RL. The effects of intermittent faults on relay RL are cumulative but this relay is adjusted so that it does not operate on the longest train of impulses sent from the outstation. A fault signal is also sent, as described below, when the spring driven transmitter requires rewinding. Transmitters, construction of, Fig. 8. A spring driven shaft i carries (1) a disc e by which the shaft is normally locked by pawl c withdrawn by magnet MA when an alarm is originated, the magnet being released by a relay operated over springs ma3 closed by pin f just before one revolution is completed ; (2) a cam disc g which changes over springs ma1 to provide a low resistance loop during impulsing and (3) the impulse wheel h controlling impulse springs ma2. When the driving spring k has expanded sufficiently to require re-winding, it closes contacts ma4 to send a fault signal to the central station. Electric selectors, Fig. 10. An electromagnetically stepped shaft sh carries a cam disc cc which in response to five and ten impulses selects springs mc1 and mc2 for closure of police and telephone call circuits respectively. When either kind of call comes in, magnet MB pulls up a holding pawl ee and impulses are repeated to magnet MC the stepping pawl ii of which is pivoted to a link oo to allow the pawl to slip back over the teeth of the ratchet wheel aa during the break periods. Traffic signal post, Fig. 11. In addition to the usual red, amber and green traffic lamps LH-LK, the post is provided with a lamp LF adapted to illuminate an " all traffic stop " indicator ba, and " all traffic stop " audible signal HA, and lamps LG, ma adapted to illuminate indicators ca . . . . fa in accordance with the location of the alarm.