Patent GB-907798-A (GB)
Title: Improvements in or relating to teleprinter systems
Inventor: HENNIG FRITZ
IPC: H03M13/51
Filed: 1959-07-23
Abstract: 907,798. Error-detecting telegraph systems. SIEMENS & HALSKE A.G. July 25, 1960 [July 23, 1959], No. 25297/59. Class 40 (3). In an error-detecting teleprinter system each character is represented by a group of code elements comprising x first code elements (which identify the character) and x further code elements. Each of the x further code elements is of the opposite kind to the corresponding one of the x first code elements. The first code elements must contain, in one embodiment, an even number of elements of one kind, or, in a second embodiment, an odd number of elements of one kind. The first and further code elements may be interleaved so that a mark signal is always followed by a space signal, and vice versa. Fig. 1 shows the transmitter of a synchronous teleprinter in which it is ensured that there is always an even number of space elements in all sets of first code elements. A five-unit signal is fed into the apparatus by tape-reader contacts F1-F5 and passed, if necessary via storage relays (not shown), to transmission distributer contacts S1-S5 and to relays A1-A5, a relay being energized if a voltage corresponding to a space element is fed to it. If an odd number of space elements is present in the five-unit signal relay B is energized and a space element potential is passed to contact S6. Contacts S1-S6 are coupled to contacts S7-S12 and the two sets feed opposite sides of the transmission relay SR so that a mark element in the set of first code elements is transmitted as a space element in the set of further code elements. The receiver, Fig. 2, comprises five distinct circuits. The first is the receiver distributer which includes the receiving relay ER and distributer contacts E1-E12. These contacts correspond to the transmission contacts S1- S12. The second circuit operates to decide whether or not corresponding first and further code elements are the inverse of each other. If, for example, the second of the first code elements is the same as the second of the further code elements relay Y2 is operated under the action of relays R2 and R8. To check that the first code elements comprise an even number of space elements the third circuit is used, in which the contacts r2b-r6b, r2c-5c are such that relay W is energized if the number of spaces is not even. The fourth circuit indicates whether, of the relays Y1-Y6, none, one, or more than one is energized. The circuit is a bridge having a relay V and a polarized relay U as one diagonal, and is balanced when one only of the relays Y1-Y6 is energized. If no relay Y is energized, relay V is energized and relay U pulls up in one direction, while if more than one relay Y is energized V is still energized but relay U pulls up in the other direction. Dependent upon the energization or otherwise of relays U, V and W, a relay Z is energized to indicate reception of a faulty signal. A final circuit comprises relays N1-N5 which control a printer or a startstop transmitter, and is such that singleelement errors are corrected automatically. The performance of the circuitry in response to various forms of error in the received signal is indicated in tabular form in the Specification.