Patent GB-664056-A (GB)
Title: Improvements in code signalling systems
IPC: H04L1/08
Filed: 1949-03-11
Abstract: 664,056. Type-printing telegraphy. TOMLINS, F. C. March 11, 1949, No. 6727/49. Class 40 (iii). [Also in Group XL (c)] A telegraph system arranged to prevent false operation of the printing apparatus due to faults in transmission, such as may be produced by atmospheric disturbances in systems employing radio channels, is provided at the transmitting station with apparatus for transmitting each element of a signal code twice, once in a normal manner and once in an inverted manner. At the receiver, the character corresponding to the code is recorded only providing a normal and inverted signal is received for each element of the code. When a normal and inverted signal are not received an error indication is recorded. The normal and inverted signals are transmitted in an interleaved manner, that is, each normal signal element is immediately followed by its corresponding inverted signal. A modified system is adapted to be switched to operate as a two-channel multiplex system without error detection. The normal signals remain under the control of a first transmitter and the inverted signals are placed under the control of a second transmitter, the two sets of signals being separated at the receiver to operate individual recorders. In Fig. 1, the conditions set up on five contacts 26-1 to 26-5 under the control of sensing t devices 24-1 to 24-5 of a tape transmitter 10 are stored on five relays 33-1 to 33-5 and cause the contact tongues 30-1 to 30-5 to move in accordance with the code to be transmitted. The front contacts are connected to normal transmitting segments 52-1 to 52-5 of a distributer 11, while the back contacts are connected to inverted transmitting segments 52-1A to 52-5A. Thus, as the distributer arm 17 traverses the segments, each element of the code is transmitted twice by transmitter 12, once in a normal manner and immediately thereafter in an inverted manner. The transfer of the condition on contacts 26-1 to 26-5 to the storage relays and the subsequent release of these relays at the correct time in readiness to store another code combination is controlled by relays 31, 36, 41, 46 operated in circuits extending through segments 28 and 40 of the left-hand portion of the distributer. The clutch start magnet 14 of the transmitter is energized from segment 18 through contact 22 closed by start-relay 19. At the receiver, Fig. 2, the signals operate receiver relay 62 and are distributed to primary storage relays 67-1 to 67-5 and 67-1A to 67-5A by segments 61-1 to 61-5 and 61-1A to 61-5A of a distributer 66 synchronized with that at the transmitter. The code stored on the primary relays is transferred to secondary storage relays 76-1 to 76-5 and 76-1A to 76-5A, this transfer and the subsequent release of the primary and secondary relays at the correct times in readiness to receive a subsequent code being controlled by relays 83, 71, 77, 70, 88, 92 operated in circuits established through segments 87, 65, 68, 82 of the left-hand portion of the distributer. The secondary storage relays have contact tongues 96-1 to 96-5, 96-1A to 96-5A, 97-1 to 97-5 and 97-1A to 97-5A. Each pair of tongues, 96-1, 96-1A, for example, when oppositely operated in accordance with the correct receipt of a transmitted element, complete the circuit of an associated code magnet 98-1, the remaining printer code magnets 98-2 to 98-5 being operated in a similar manner. When the signals are received without error contact tongues 97-1 and 97-1A are always oppositely operated and since the remaining contacts 97-2 to 97-5 and 97-2A to 97-5A operate in a similar manner, the circuit remains completed to an error-controlling relay 99. However, if interference or other conditions cause a pair of contacts to operate to like positions the circuit is broken releasing relay 99 and completing a circuit for error indicating magnet 101. The code magnets 98-1 to 98-5 control the setting of code bars 103, of a selector 102 similar to that disclosed in Specification 220,280, [Class 100 (iv)]. A sixth error indicating bar 104 is controlled by magnet 101 and when operated causes the printing of an error indication and blocks printing of normal characters. Multiplex system. In a modified arrangement, Figs. 3 and 4 (not shown), switching means are provided for converting the singlechannel error indicating system into a twochannel multiplex system without error indication. At the transmitter two type transmitters are provided and the connections from the inverted transmitting segments of the distributer are transferred from the back contacts of the storage relays associated with the first transmitter to the back contacts of storage relays associated with the second transmitter. The two transmitters are run in synchronism by connecting their start clutch magnets and timing relays in parallel to the respective segments of the left-hand portion of the distributer. In this manner code signals from the two transmitters are transmitted in an interleaved manner, the elements from the second transmitter being inverted. At the receiving apparatus, two recorders are provided to transfer the connections of the contact tongues 96-1A to 96-5A of secondary storage relays 76-1A to 76-5A, Fig. 2, from the contact tongues 96-1 to 96-5 of relays 76-1 to 76-5 to the code magnets of the second recorder. Since the second channel signals are inverted it is necessary to reverse them and this is effected by extending the connections through back contacts instead of front contacts. The error printing code magnet of the first receiver is disconnected. With this modified arrangement it is possible to run the transmitter as a single channel error indicating system and to operate the receiver as a two-channel system, the two recorders then printing identical characters.