GB841412A - Improvements in or relating to teleprinter systems - Google Patents

Abstract

841,412. Printing-telegraph systems. SIEMENS & HALSKE A.G. April 8, 1958 [April 4, 1957], No. 11069/58. Class 40(3). In a teleprinter system including a traffic transmitter and a service transmitter at one station, and at another station a traffic receiver and a service receiver, with interconnection between the stations by one or more channels, a device provided at the one station includes a change-over switch for selectively coupling the traffic transmitter and service transmitter to a channel, transmits a number of first idler signals during the period in which the channel is being changed over from the traffic transmitter to the service transmitter and transmits a number of second idler signals during the period in which the channel is being changed over from the service transmitter to the traffic transmitter, and a further device provided at the other station is responsive to the first idler signals to couple the channel to the service receiver and responsive to said second idler signals to couple the channel to the traffic receiver. The system described employs an errordetecting 7-unit code of 4 marks and 3 spaces, and two 7-unit idler signals designated α and #. If a service signal is to be sent in lieu of a normal message from a transmitter TG a manually operated switch (not shown) operates the device TU so that the second idler signal # is transmitted, and with the switch t in the opposite position, the service message is sent from a punched tape transmitter of the device TS. At the receiver the reception of the repeated # signal operates a circuit to switch over at contact t the normal receiver TG to the receiver of the device TS which now accepts the service message. At the end of the service message, the switch of the device TU is operated so that the tape transmitter of the device TS is disconnected, at least three idler signals α are transmitted, and the tape transmitter of the device TG is connected for normal telegraphic traffic. The reception of the successive idler signals α is effective to change over the contact t of the device TU so that the channel of the multiplex receiver MK is now connected to the receiver of the device TG. The change-over switch includes a plurality of relays each providing a delay whereby the first or second idler signals are transmitted at least three times before the switch changes over. In a multiplex system, the service signals may be sent over the associated traffic channel, or over a channel which, at the time, is not carrying telegraph traffic.