Patent GB-799301-A (GB)
Title: Improvements in or relating to electric telegraph systems and apparatus for code conversion
Inventor: DUUREN HENDRIK CORNELIS ANTHON
IPC: H04L1/00
Filed: 1953-11-16
Abstract: 799,301. Type-printing telegraphy. STAATSBEDRIJF DER POSTERIJEN, TELEGRAFIE EN TELEFONIE. Nov. 11, 1954 [Nov. 16, 1953], No. 31756/53. Class 40 (3). In a telegraph system in which the information signals to be transmitted are represented by the normal five-unit code of equal marking and spacing elements, a converter in the transmitting arrangement changes the five-unit code into a six-unit, or group, code which, for the majority of the signals, preserves the identity of the corresponding five-unit signal, and an additional element is then added to produce a corresponding seven-unit equal-ratio code, and at the receiving station the signal is tested for its correct mark space ratio and passed to a converter reproducing the original five-unit signal which, with the addition of start and stop elements, is passed to a teleprinter. As indicated by the table, Fig. 1, the five-unit combinations having two or three marks such as Z, H, G, U, &c. have a space as the added element p, whilst those having one marking element, such as T, E, have a mark element as prefix. The characters with four marking elements, such as Q, X, V, K, have two of these elements changed to spaces and the prefix element p as a mark. The " allmarking " letter-shift signal has its first, third and fourth elements changed to spaces, and a prefixed marking element, whilst the all-spacing signal (unperforated tape) has its fourth and fifth elements changed to makrs with a mark element as the prefix p. Transmitting-arrangement. The impulses from the perforated-tape transmitter TR are fed by means of pulse generators P, P1 to triggers CT1 ... CT5 and to a code converter CC from which pulses are fed back under control of generator P2 to the triggers and to a trigger CT6 which determines the polarity of the first element and is normally in the condition to provide a space. The elements are passed to triggers A, B ... F under control of a timing circuit Scp, and simultaneously to an output trigger circuit ST whose output is fed to a mark counter MC normally in condition to feed a mark to the seventh trigger G. In response to two marks, the counter is restored to its original condition, and if three marks have been detected the condition of the counter is reversed so that a space is applied to trigger G and to the trigger ST for the transmission of the seventh element. The majority of the signals pass through the converter CC unchanged and have a spacing element prefixed by the trigger CT6. During the intervals between traffic transmission, 6-unit idle time signals are generated under control of the device It. The circuit shown in Fig. 14 is incorporated to deal with the signals which have their five-unit codification changed and those which have a marking element as prefix. In the case, for example, of the letter Q represented by + + + - +, the triggers a, b, c, d, e have outputs a1 b1, c1, d11, e1 positive so that a positive pulse at p3 renders the rectifier network Q conductive and positive pulses are applied over conductor p to the prefix trigger p to produce a + ve (mark) pulse at output 61 and over conductors a, b to the second input of trigger a, b to provide negative (space) pulses at outputs 62, 63 so that the resulting six-unit signal from the output terminals 61 ... 66 is + - - + - +. For the signals line feed space and letter E, a pulse is applied over conductor p to reverse the trigger p. For carriage return and T, the trigger p is reversed, but the pulses applied over d, e are without effect. For the all marking lettershift signal conductors a1, b1, c1, d1, e1 of the triggers a ... e are positive so that networks X, K become conductive with positive pulses on p, a, c, d, so that the derived six-unit signal becomes + - + - - +. In the case of the allspacing signal, the outputs a11, b11 ... e11 of the triggers are all positive so that the rectifiers CR and T conduct and apply positive pulses to conductors p, d, e reversing triggers p, d, e to form a six-unit signal + - - - + +. A service signal and two idle-time signals α, # are generated in the auxiliary transmitter It and fed directly to the triggers CT6, CT1 ... CT5 through the circuit CC without change and thence to the triggers A ... F. Receiving-arrangement. The received signal elements are passed to trigger TR7 and in succession to triggers TR6 and triggers TR1 ... TR5 under control of pulses from generator P1r. The signal elements from TR7 are also passed to a circuit SC which examines the mark-space ratio of the received signals. The received pulses pass to the code converter CCr from which pulses are fed back under control of generator P2r to the triggers TR6, TR1- TR5 from which they are passed under control of a generator P3r and trigger circuits A ... G forming a distributer to a trigger circuit TS and printer Pr, a stop pulse being provided by a device SP under control of the trigger G controlled by the generator P3r. The code converter CCr includes the circuit, Fig. 16, which restores to their original form those 5-unit signals which have four marking elements, the letters-shift signal, and the all-spacing signal. The six-unit code for the letter Q is + - - + - + and as the reversed outputs from the conductors p1, a1, b1 ... e1 of the triggers p, a, b, c, d, e are passed to the rectifier networks, negative pulses will be derived from the conductors p1, c1, e1 of the triggers p, c, e, so that a negative pulse from the source p2, r1 causes negative pulses to pass over conductors a, b to the righthand inputs of triggers a, b which are reversed to provide positive outputs on conductors 2 and 3, the outputs on the conductors 4, 5, 6 being + - + respectively, so that the reformed fiveunit signal is + + + - +, with the prefixed marking element changed to spacing by the positive pulse p2, r2 passed over p to the r.h. input of the trigger p to provide the start element of the five-unit combination. In the case of the idle-time signal B, the outputs at the l.h. terminals are - + + - - + so that p1, c1, d1 are all negative and the network Z passes negative pulses to the r.h. inputs of triggers a, b, c with the result that the signal at terminals 2 ... 6 is +++++. As the idle-time network Z is negative, the positive pulse p2, r2 cannot pass to the r.h. input of the trigger p so that the normal negative start element is not produced.