Patent GB-330881-A (GB)
Title: A telephone and signal system for fire alarm, police, and ambulance call, and the like
IPC: H04M11/04
Filed: 1929-03-14
Abstract: 330,881. Doig, P. March 14, 1929. Fire, police, and like alarm system and apparatus.-In a telephone or signaling system for fire alarms, police and like calls, employing call boxes for communication with a central station, means are provided whereby the calling apparatus at a box can only be used when the door of the box is closed, and when the apparatus is used the door is automatically electrically locked. In the construction shown in Figs. 1 and 2, the door bolt 105 connected to an iron core 102 is located within a solenoid 104 which is energized when the door of the call-box is shut and the telephone receiver is removed from the switch hook, so that the bolt is shot, against the action of a spring 103, the bolt passing through a hole 114 in the striking plate 121 and through a hole 118 in a slidable guard plate 123. The core 102 controls contacts 110 which are closed when the solenoid 104 is energized. The guard plate is connected to a core 115 in a solenoid which is actuated when the door is open so that the guard plate is raised to cover the bolt hole and prevent tampering therewith. The switch-hook, Fig. 3, is provided with a slidable forked member 132 adapted through solenoid action to be advanced when the door is open whereby the longer limb of the member 132 bridges the extremity of the switch hook and prevents removal of the receiver, and the shorter limb passes below a stop 135 and prevents pivotal movement of the hook. When a person enters a call-box, the circuits in which are shown in Fig. 4, the action of opening the door opens contact S1 and closes contact S2, the latter completing a circuit for solenoids SL, SG. The solenoid SL operates to lock the receiver and solenoid SG to lift the guard plate. These solenoids are de-energized when the door is closed, and contact S1 is closed, whereby the circuit of a solenoid SH is completed when the caller removes the receiver so that the bolt is shot to lock the door. The solenoid closes contacts sh1, sh2, the former closing a circuit to control the solenoid independently of the switch-hook and door contacts. Contact sh2 closes a circuit for a lamp L2 outside the call box. The removal of the receiver completes a circuit to the central or police station, Fig. 7, through both windings of relay LA causing lamp L4 to glow. Communication is established by the operator at the police station inserting plug PX, Fig. 10, into jack J1 and throwing key K10 leading to his telephone circuit. If the call is to be extended to a message stall plug PY is inserted into jack J2, Fig. 11, and calling key K11 is thrown. Alternating current is transmitted from battery-connected generator G1 through a circuit including interrupter INT1, plug PY, jack J2, switch-hook contact sw1, Fig. 12, and relay NA, the latter closing a circuit through a lamp L17 or, if liev K17 is thrown, through a buzzer. BZ. The operator at the message stall, by throwing a key E16, may close a circuit through winding 33 of induction coil ID for apparatus which makes a phonographic record of the conversation. The message, stall operator may call the police station by removing the receiver, thereby closing a circuit through lamp L16, which glows until the police station operator inserts plug PX, communication being established when he throws key K10. Means for unlocking the door of the call-box. The call-box may be opened from the inside by means of a key adapted to open key contact K4, Fig. 4, whereby the circuit of solenoid SH is broken. A person inside the call-box who does not possess a. key for opening contact K4 is released by means controlled mainly from the police station. The caller presses a key K8 and the operator at the police station presses a key K9, Fig. 10, which connects a high voltage battery 39 to the calling line, thereby closing a circuit for a slow-acting relay O. The relay operates contacts o1, o2, the former opening the circuit of solenoid SH, and the latter permitting an increase of current to operate means for releasing the key K9. An occupied call-box may be entered by a person possessing a key which opens contact K5 from the outside, thus opening the circuit through solenoid SH. Indicating faults in the line wires. The battery at the police station for supplying current to the relays, &c., has a centre-point tapping which is earthed. A high resistance loop circuit is provided on each line and, as shown, includes the upper winding of relay LA, Fig. 7, upper winding of relay V, impedance IB, Fig. 4, lower winding of relay V, and lower winding of relay LA, leading to the negative pole of the battery. Relay V in this circuit does not operate as its windings are in opposition. Relay LA owing to impedance IB operates only partly but sufficiently to open contact la1. In case of disconnection on the line contact la1 is released to close a circuit through lamp L3 and a relay PA, causing the lamp to glow. In the case of a short circuit relay LA will operate fully, causing contact la2 to close a circuit through lamp L4. When an earth fault occurs one winding of relay V will receive more current than the other and the relay will operate to actuate contacts vl, v2, v3. v1 opens and prevents lamp L3 from glowing. If the earth fault is in line 4 contact v3 opens a circuit through relay LA and closes a circuit through relay HB whereby contact hb2 is closed, completing a circuit through lamp L5. If the fault is in line 31 contact v2 completes a circuit through the upper winding of relay HA so that contacts ha1 and ha5 are closed. Contact ha1 marks conductor 7, Fig. 8, connected to a bank contact of a finder switch controlled by magnet MA. Contact ha5 closes a circuit for a relay FG, the contacts of which close circuits for magnets such as MA relative to different junction circuits. The magnet energizes and opens its own circuit by its contact mal; it then releases and moves its wipers on to the next contact. This stepping action is continued by the various switches relative to the junction circuits until the faulty line for example the line 7 shown in Fig. 7, is found by one of the switches. A circuit is then completed which includes both windings of relay KA, and lower winding of relay HA, so that contact ka2 closes to complete the circuit of lamp L6. Calling-substation from central station. The operator at the police station inserts a calling plug PY, Fig. 10, into jack J1 and throws one of the calling keys K11, K12, K13. The call-box, for example, that shown in Fig. 4, has a polarized relay P responding to alternating current of a certain frequency, which is transmitted, when the police station operator throws a key E11, in a circuit including a generator G1 for the required frequency. Relay P thereupon vibrates its armature extending the circuit to relay N which locks up through contact n<1>, opens contact n<2> to release relay P, closes contact n3 to light a lamp L2 and closes contact n4 to operate an electric horn 21. The signal is interrupted by an interrupter INT1, Fig. 10. In case of an urgent call K15 may be thrown to interrupt current in a different way by means of interrupter INT2. When the call is answered the removal of the receiver acts to release keys K11, K15. Keys such as K12, K13 are provided for calling other boxes, these keys acting in conjunction with generators of different frequencies. Key K15 may be thrown in case of urgency when calling any box. Calls to fire station. Calls to the fire-station are routed by way of the police station by junction circuits one of which is shown in Figs. 8 and 9. Relay LB is normally partially operated so that contact lb1 is open. If the junction is disconnected the relay is released to close the contact so that lamp L8 glows. To make a fire call a slow-returning key K7, Fig. 4, is depressed disconnecting from the loop circuit contacts 53, 12 and impedance IB, and causing earthing of the conductor 2 so that the calling line is extended by way of contact and wipers ma3, Fig. 8, resulting in relays KA and HA, Fig. 7, being operated. The connections of contacts ha6 and ha7 to the upper winding of relay V are reversed, causing the relay V to operate. These relays effect the operation of relay A, Fig. 8, which at contact a1 completes a circuit for lamp L7. Contacts a2 and a3 short-circuit resistances R4 and R3 to increase current through relay LB, Fig. 9, whereby its contact lb2 closes a circuit through calling lamp L9 and relay PB. This relay at contact pb1 completes a circuit for L18 or audible alarm 54, depending upon the position of key R3. The fire station attendant throws key K2, putting the telephone set into circuit. When conversation is finished, the attendant momentarily operates key K1 to render inoperative relays KA, HA and V and restores key K2 to normal. The attendant at the police station instructs the caller to operate key K8 and restore the receiver and he himself operates key 9 to unlock the door of the call box.