Patent GB-171129-A (GB)
Title: Improvements in telephonic call systems
IPC: H04Q5/00
Filed: 1920-06-10
Abstract: 171,129. Hastings, R. C. M. June 10, 1920. Party-line systems and apparatus.-Telephonic call arrangements for a system containing a receiving station and a plurality of substations for the transmission of intelligence, for example by telegraph, in which a substation, on lifting its receiver off the hook, is connected to and signals the receiving station, the remaining substations being automatically locked from the line until the receiver has been replaced or the substation has been shunted, comprise means operable from the receiving station for giving an audible alarm at the substation if the replacement of the receiver has been neglected, and means for shunting such a substation until such neglect has been remedied. When the line is free, current flows from the low-voltage battery 1 at the receiving station E through the electromagnet 3 which is energized, the bridge contact 5 carried by the armature 4, the armature 11, lines 12 and 13, and through the substations S<1> by way of electromagnets 15, which are not sufficiently energized to move their armatures a, contacts 17, receiver hooks 18 and conductors 19 back to the battery 1. When the receiver R at the substation S<1> is removed from its hook, this circuit is broken and an alternative path through the substation is made, comprising the receiver R, armature 24, transmitter T, contact 27, and receiver hook 18 to conductor 19. The breaking of the circuit causes the electromagnet 3 to be de-energized, and the armature 4 moves across to break the circuit at the bridge-piece 5, and to close the switch 30 and to be itself connected to the contact 36. The latter connection completes the circuit of the operator's signal lamp 41 from the battery 43. The closure of the switch 30 connects the high-tension battery 33 to line, and the electromagnets 15 in all the substations, except the calling substation, being thereby energized, attract their armatures a which carry bolts 78, the ends 80 of which engage lugs 81, thus locking the corresponding receiver hooks in their lowest positions. The bolts may carry visual indicators 100 to indicate when the line is engaged. The insertion of the plug J into the socket J<1> by the operator at the station E completes a circuit from the battery 43 through the lines 12, 13, the instruments T<1>, R<1> and the electromagnet 49, which is energized and attracts its armatures 11, 39 thus breaking the circuit of the signal lamp and connecting the battery 43 to line through the operator's instruments. When the conversation is completed and the plug J withdrawn, the operator at station E momentarily closes the contact 53, 54 to energize the magnet 56, which restores the armature 4 to its original position before calling. The operator also closes the switch 60, 61, and if the receiver at any substation S<1> has not been replaced on its hook, a circuit is completed in that station from earth g and the alternating-current generator G through the condenser 64, call-alarm 65, which is sounded, electromagnet 67, contacts 69, 70 bridged by the raised receiver hook, and to earth g<1>. The armature 24 of the electromagnet 67 breaks the receiver circuit at contact 23 and closes a contact 84, 85 which shunts the substation from the line. A projection 74 on the hook 18 engages a spring-pressed locking member 73 on the armature 24, thus holding the armature in the above position until the hook is depressed by the restoration of the receiver. Alternating-current or direct-current electric motors may replace the electromagnets.