Patent GB-642244-A (GB)
Title: Improvements in or relating to printing telegraph systems and apparatus
IPC: H04L25/49
Filed: 1946-09-12
Abstract: 642,244. Type-printing telegraphy. RADIO CORPORATION OF AMERICA. Sept. 12, 1946, No. 27491. Convention date, May 23, 1945. [Class 40 (iii)] A printing telegraph system employs a five-unit code in which the code combination for each character comprises three elements or units which are positive or negative relative to a zero condition and the remaining two units are represented by the zero condition. In a modification employed for frequency transmission, the positive and negative pulses are transmitted as frequencies above and below a mean or basic frequency which represents the zero condition. Transmitting - arrangements. In one construction, Fig. 3, five pairs of pecker pins 11, 13 disposed transversely across a perforated tape 12 and selectively actuated by the perforations connect a positive or negative source via a contact 3 to a distributer 16, Fig. 2. The operated peckers are restored to their normal position by a bar 17 operated by a member 19 at the end of a signal. The second pin of each pair may be disposed longitudinally of the tape, or, in a modification, the five pairs of pins may be disposed to co-operate with a single longitudinal row of holes. In the twochannel arrangement of Fig. 2, the zero, positive and/or negative conditions set up on the transmitter 14 are sequentially passed by segments 1 ... 5 of the channel distributers to a polarized relay 20 having an armature 21 with a neutral position and connections 22, 24 established in response to the positive or negative impulses. A predetermined frequency generated by the oscillating circuit 26 when the armature 21 is in its neutral position is increased or decreased, preferably by equal amounts, when the armature contacts the respective connections 22, 24. At the receiving station, Fig. 4, the received frequencies are detected and fed to a discriminator circuit 28 whose output in the form of positive, negative or zero current controls a polarized relay 29 whose armature 30 is connected to battery 33 and to a point common to two coils 37, 38 of a relay 36. The contacts 31, 32 engaged in response to positive or negative pulses complete a circuit through a ring C and a segment of an inner ring E to the coil 37, or through a ring D and a segment of an outer ring F to the coil 38. A relay 36 is provided for each of the five code selector bars 39 which have a neutral position and a left-hand or right-hand operated position corresponding respectively to the operation of the coils 37, 38. The character to be selected is determined by the movement of a type-bar into an aligned,set of notches 41 in the code bars 39, and, after the printing or equivalent function, a wedge member 43<SP>1</SP>, preferably operated by an electromagnet, engages triangular recesses 43 in the code bars 39 so that those moved to the right or left in response to the preceding signal are restored to their neutral position. The receiver may be cornbined with error-detecting apparatus brought into operation when more or less than three selecting impulses, i.e. impulses other than the zero impulses, are received, and in this connection Specification 480,150 is referred to.