Patent GB-899293-A (GB)
Title: Improvements in or relating to teleprinter signal transmission apparatus
IPC: H03M5/00
Filed: 1959-04-01
Abstract: 899,293. Teleprinter transmission apparatus. SIEMENS & HALSKE A.G. April 1, 1959 [April 2, 1958], No. 11050/59. Class 40(3). In a teleprinter signal transmission apparatus comprising a machine for reading a tape carrying code combinations according to a first teleprinter code and provided with switching means settable to reproduce said first teleprinter code in association with a converter which translates signals in said first code to signals in a second code and has its input and output connected respectively to the output of the tape-reading machine and to the input of a store which consists of a plurality of storage elements, each of which has two stable states of which one is the rest or normal state, and the rest state of the store is arranged to correspond to a combination of teleprinter signal elements of the second teleprinter code. In the arrangement, Fig. 2, the operation of a tape reader LG selectively applies potentials to the input terminals 1Z, 1T . . . 5Z, 5T of a code converter CU translating to a 3:4 equal ratio code and having seven pairs of output terminals of which solely the terminals 1T<SP>1</SP>, 2Z<SP>1</SP>, 3T<SP>1</SP>, 4Z<SP>1</SP>, 5Z<SP>1</SP>, 6T<SP>1</SP> and 7T<SP>1</SP> are employed. The store to which the output of the converter CU is applied comprises seven bistable devices S1 ... S7 of which the hatched portions are normally rendered conducting by pulses P1, Q1, after the 7-unit code has been utilized for transmission and correspond to the 7-unit signal of the continuous signal of one polarity including start and stop elements employed in the 5-unit code during a pause in transmission. For the translation of a normal 5-unit signal to the corresponding 7-unit code combination, voltage pulses will be applied solely to those terminals which require change-over of the devices S1 . . . S7 from their rest conditions and the change-over will be effected by operating pulses P2. For example, the 7-unit signal for the letter G is TTZZZZT, so that pulses will appear solely at those terminals of 1T<SP>1</SP>, 2Z<SP>1</SP> . . . 7T<SP>1</SP>-namely 1T<SP>1</SP>, 4Z<SP>1</SP>, 5Z<SP>1</SP> and 7T<SP>1</SP>-which necessitate a change-over of the normal conditions of the devices Sl . . . S7 when the pulses P2 are applied. In the modification, Fig. 3, the converter CU produces the first six-elements of the corresponding 7-unit code, and the transmitter arrangement includes an assessor device which adds a space or a mark to provide the predetermined mark-space ratio in the 7-unit signal. As indicated the devices S1 . . . S6 are normally in the condition corresponding to the signal of one polarity indicative of a pause in transmission. The six elements may be set to a normal rest condition corresponding to the clearing signal of the other polarity continuously applied by the operation of a double switch S5d which applies earth to side T of S5 and a pulse Q2 to change S5 to the condition Z, this being the only change required in the first six elements of the corresponding 7-unit signal. In view of the change of the 5th unit to Z, the assessor will change the 7th unit to T to preserve the 4Z: 3T ratio. The change of the 5th unit may be effected by a changeover switch S5w operated in lieu of the switch S5d. In a modification, Fig. 4 (not shown), in which the tape-reader is at an appreciable distance from the code converter and transmitter, the input to the converter is taken in parallel form from the output of a device which has as its input pulses received in serial form from the distant transmitter. In this modified arrangement, the converter, similar to CU of Fig. 3, provides solely the first six elements of the 7-unit code, an assessor being provided to add the 7th element. In this arrangement the element S5 is normally in the "T" condition, but is changed over by an "OR" gate which passes a pulse to change over the element to the "Z" condition in response to a pulse from terminal 5Z<SP>1</SP> or a pulse from an appropriate terminal of the device providing the parallel output from the serially arranged signals.