GB526988A - Improvements in or relating to printing telegraph receiving apparatus - Google Patents

Abstract

526,988. Type-printing telegraphs. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. March 30, 1939, No. 10018. Convention date, March 30, 1938. Addition to 514,588. [Class 40 (iii)] In a development of the invention contained in the parent Specification an error detecting device comprises a plurality of parallel circuited resistances, a relay system operable in series with a selected number of the resistances, means, directly operable by the code bars of the receiver, for energising the relay system through the resistances and means controlled by the relay system for indicating a departure from a prescribed number of code bar operations by a received code combination. The system described relates to code combinations of seven impulses of which three are marking impulses. Code bars 7, Fig. 2, set in turn by the received impulses close individual contacts 11, 13 if the appropriate impulse is of marking nature. Each contact has an equal resistance 21 in series with it and all are connected in parallel and through relays 27, 29, 31 in series to earth and positive battery. The relay contacts are connected as shown to a solenoid 35 and their windings 27, 29, 31 are such as to pull up on passage of current corresponding to less than three, three and more than three closed contacts 11 respectively. Their interconnection is such that a completed circuit for the solenoid 35 is only provided if three marking impulses are received. The energization of the solenoid 35 prevents the operation of an error indicating type-bar which is operated under all other circumstances. If a switch 55, connected to the relay 27, is opened the error indicating type-bar is operated when no marking impulses are received in a given combination and may thus be used to indicate fading during reception of a monitoring idle time signal.