Patent GB-795027-A (GB)
Title: Improvements in or relating to teleprinter communication systems
Inventor: WALLENS ANTHONY WALTER
IPC: H04L17/16
Filed: 1956-05-24
Abstract: 795,027. Printing telegraph systems. CREED & CO., Ltd. May 24, 1956, No. 16061/56. Class 40 (3). A teleprinter in a teleprinter intercommunication system is associated with a control circuit which incorporates means for arresting the selection mechanism of the teleprinter receiver in the stop position after the receiver electromagnet has been in the spacing condition for a predetermined time. The invention is described for a teleprinter system comprising a number of stations in a loop and in which a station can transmit a message to selected stations with the exclusion of the others. Initially, the operator at the calling station transmits a signal designating his station, and at all stations the operation of the receiving magnets 47 operate a lever 15 and detent 12 so that a projection 14 is moved away from the lug 10 on a pilot cam 9 having a projection 11 which through a roller 23 rocks an arm 26 connected to a shaft carrying a detent member which controls the rotation of the selector cam sleeve of the receiver. The instant at which the cam sleeve is released in relation to the release of the pilot cam 9 can be adjusted by circumferential movement of the roller 23 by means of the support 18 in an arcuate guide member 19. Stations are selected for communication by transmitting appropriate character signals which close contacts 42, Fig. 3, in each of the associated control circuits so that a relay A is operated and locks up over contact A1. Following the calling signals, the transmission of the " Bell " signal closes contacts 43 so that a relay B is operated in the control circuits of those stations not selected for communication. Relay B locks up over contact B1 and at contact B2 the transmission contacts 40 of a station are shortcircuited. At contact B3 the receiving magnet 47 is disconnected from the response of the receiving relay D. The grid of a valve V1 is normally negative, but becomes positive via resistor 46 and capacitor 45 when the armature D1 has remained on the space contact S for a considerable period, e.g. half a second. The valve V1 becomes conductive, operates relay C which at contact C1 operates a solenoid 50 actuating a lever 28 carrying a projection 32 which engages the lug 10 to arrest the pilot cam 9 near its stop position so that the arm 26 is in the position to arrest the selector cam sleeve. The operation of relay C opens the circuit of relay A which releases when the line is restored to mark, the armature D1 opens the anode circuit of the valve V1 and relav C releases so that the circuits at the intercommunicating stations are restored to normal. The release of the solenoid 50 allows the pilot cam 9 to move so that the lug 10 engages the projection 14, but this is without effect on the selector cam sleeve. Also, at the excluded stations the valve V1 is operated by the long spacing signal and the operation of relay C opens the circuit of the relay B and also energizes the solenoid 50 so that the selector cam sleeve is brought to rest in the stop position by the arrest of the pilot cam 9.