Patent GB-529848-A (GB)
Title: Improvements in or relating to printing telegraph transmitter apparatus
IPC: H04L17/06
Filed: 1939-05-26
Abstract: 529,848. Printing telegraph transmitter. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. May 26, 1939, No. 15706. Convention date, May 28, 1938. [Class 40 (iii)] Relates to printing telegraph transmitters controlled by a perforated tape and sending signals in the so-called 7-unit equal length printer code in simplex or synchronous multiplex systems especially for use with a radio channel. According to the invention, means are provided for sending (1) an " idle-time " signal, during which the radio channel may be " monitored," and (2) auxiliary or " service " signals useful for indicating starting and stopping periods in the transmission of " traffic " signals as well as for indicating departures from normal conditions. Means are also provided to stop the feed of the tape if the slack thereof is reduced below a given value. As shown, the tape feed mechanism 35 and the seeker pins 71 cooperating with the tape are driven synchronously with the multiplex signal distributer D by an electromagnet 34. The " traffic " signals from the tape control a transmitter T comprising seven switch tongues 8 operating between positive and negative contacts 9, 10 and connected to contacts on the distributer ring R1 co-operating with a brush 11 leading to collector ring R3 connected to line. The electromagnet 34 operating the tape mechanism is controlled by contacts 8, 9, 10 on the distributer ring R2 co-operating with a brush 12 leading to a collector ring R4 connected to positive of battery B. " Idle-time " signals are sent by closing a manual switch MS to energize a relay 16 controlling contacts 13, 14, 15, which thereby break the connections between certain contacts of the distributer ring and their corresponding tongues 8 of the " traffic signals transmitter T and establish direct connection of these contacts with positive of battery B. The manual switch MS is mechanically linked with the operating mechanism of the transmitter T in a known way so that the switch can be closed only upon completion of the transmission of a given character signal. Auxiliary or " service " signals are sent by cams C1 ... C5 adapted when operated to break connection from certain contacts of the distributer ring R1 and the corresponding tongues 8 of the "traffic" signals transmitter T and establish direct connection of these contacts with, positive of battery B. The cams are driven by a spring 60 through ratchet 58, 61 and gearing 56, 54 and move step by step under the control of an escapement 55 commanded by an electromagnet 62, which is energized once at each revolution of the distributer. Four steps are used for a complete service signal comprising " shift," " bell, " unshift," and return to normal inactive position. This combination signal may, however, be repeated a number of times. This " service " signal is initiated by a dialling device 50 operated by a finger in one of the holes 51 for winding up the spring 60. The hole selected determines the number of times the combination signal will be transmitted. When the dial is thus operated an arm 59 on its spindle causes a switch member 43 to move from a contact 44 to a contact 69, thereby breaking the circuit of one half of a relay 40 and making the circuit of relay 62. The relay 40, now unbalanced, attracts its armature 48 which establishes permanent connection of electromagnet 34 to battery B, so that step by step operation of tape mechanism is suspended until the " service " signal has been sent and the dial has returned to normal position. Tape slack device. The circuit of half of the balanced relay 40 includes a switch 46, 47, which is opened if the slack in the tape is reduced beyond a given point. The relay, being then unbalanced, attracts its armature 48 which connects electromagnet 34 permanently across battery B, so that the step by step operation of the tape feed ceases.