Patent GB-930384-A (GB)
Title: Improvements in or relating to electric telegraph regenerative repeaters
Inventor: HAKIM SAHIR SABIR
IPC: H04L25/24
Filed: 1960-05-04
Abstract: 930,384. Telegraph regenerative repeaters. GENERAL ELECTRIC CO. Ltd. May 2, 1961 [May 4, 1960], No. 15763/60. Class 40À(3). [Also in Group XL (c)] A regenerative repeater for a start-stop system comprises a counting unit which is operated in response to a received start signal and which produces pulses used for timing regenerated outgoing signals. An outgoing stop signal is transmitted a predetermined time after the start signal whether or not an incoming stop signal has been received, whereupon the counter is stopped. Long space signals are recognized by the absence of a mark during said predetermined time, and in such a case no outgoing stop signal is transmitted until the end of the long space. Short start suppression is provided. Normal operation.-Start-stop telegraph signals are fed in at 47. These are as A, Fig. 3, and after differentiation at 51 are passed as B to bi-stable unit 22. This gives a waveform C which comprises a long positive pulse which ends when the automatic stop signal is inserted. Gate 45 now releases a series of bi-stable triggers, or binaries, 23-28 which act as frequency dividers for a square wave generator 49. The output of binary 29, fed to unit 56, is as D and passes to a space detector gate 58 as E. Gate 58 is also fed with signals A and is such that the output is as F, i.e. is a positive pulse at the start of each positive telegraph pulse. The output D<SP>1</SP> from the other side of binary 29, the inverse of D, is fed as H to a mark detector gate 110 which gives pulses I corresponding to negative telegraph pulses. The two sets of pulses F, I are fed as G, J to opposite sides of binary 40 which operates a bi-stable device 48, e.g. a polarized relay, so that the output waveform is as K. Short start suppression.-The waveform derived from the output of binary 29 and fed to binary 30 is as L, and results in the waveform M at the output of binary 32. This is fed as N to a fault detection gate 134, which also receives the incoming telegraph signals and which will not pass signals when the telegraph signal has start polarity. If the telegraph input to gate 134 is in the form of a spurious signal lasting less than 10 m.sec. gate 134 will not pass this short start pulse, but it will pass the pulse N which occurs after the short start pulse has ended and the incoming line has reverted to mark condition. Pulse N therefore passes through gate 140 and closes binary 22 and the whole operation of the repeater ceases. Generation of stop signal.-Waveform Q from binary 31 appears at the output of binary 33 as R. A differentiating circuit 165 derives a signal S from A, and both R and S are fed to binary 34. This results in T at the output of binary 34, and the waveform passed to an OR gate 149 is as U. The input of binary 36 is also U and results in V being fed to AND gate 154. Gate 154 is also fed with W derived from binary 26 of the frequency dividing binaries. The output X of gate 154 is divided by binaries 37, 38, 39, unit 160 thereby producing pulse Z which closes binary 22, hence closing down the whole apparatus and thereby setting the line to the mark condition. Long space signal.-A long space signal has a duration greater than 130 m.sec. and is as AA, Fig. 3c, when received at 47. It appears at the input of binary 35 as BB. Further, binary 22 having been triggered at the start of the long space, binary 35 will receive waveform R from binary 33. The combined effect of R and BB on binary 35 is to produce CC at its output. OR gating circuit 149 receives both CC and U, and passes waveform DD which causes binary 36 to produce EE. AND gate 154 is supplied EE and W so the output of 154 is as FF. By division in the binary chain 37, 38, 39 and by differentiation pulse II is produced and fed to gate 140 which passes JJ to binary 22, thereby causing the repeater to be set to its idle state and a stop pulse to be transmitted.