Patent GB-670579-A (GB)
Title: Apparatus for compensating for telegraph distortion
IPC: H04L25/03
Filed: 1948-01-26
Abstract: 670,579. Code telegraphy. BAYARD, H. M., and ROQUET, R. J. C. Jan. 26, 1948 [March 3, 1947], No. 2279/48. Class 40 (iii). In an arrangement for the precorrection of signal elements transmitted over a line, the delay imposed on each characteristic instant of the transmitted modulation is determined by taking into account at each characteristic instant a selected number of the signal elements which precede the characteristic instant ("preceding elements") and also a selected number of the signal elements immediately following the characteristic instant (" subsequent elements "). In the embodiments described the train of preceding and subsequent elements is registered and analyzed in respect of the delay necessary and the characteristic instant with its appropriate delay is applied to the transmission line in the period between the beginning and end of the period of the final subsequent signal of the sequence whose characteristic element is to be precorrected. In the arrangement shown in Fig. 5, applied to bivalent modulation and comprising three preceding elements and two subsequent elements, in which five successive elements recorded by a relay ME are applied by a distributer Do having individual segments Po<SP>1</SP> ... Po<SP>5</SP> to relays R1 ... R5. The armatures of the relays R1 ... R5 are connected as shown to separate segments of five distributers having brushes D1 ... D5 which simultaneously rotate over the segments of the distributers. A sixth distributer has a brush D6 engaging segments displaced in the direction of rotation relatively to the simultaneously engaged segments of the five distributers. The continuous rings of the distributers are connected to relays R6, R7, R8 which are selectively operated according to natures of the five elements. For example, if the first and second subsequent elements are of the same polarity, relay R8 is not operated, but if of different polarity R8 is operated. The selective operation of the relays R6, R7, R8 connects a path from contact K and condenser C via one of eight resistances r1 ... r8 to a transmitting relay RE which is actuated to the position corresponding to the polarity of the signal element by a relay R9 energized over a segment of the sixth distributer in accordance with the signal element following the characteristic instant and set up on one of the relays R1 to R5. A modification having relays similar to R6, R7, R8, forming a selective path through relay contacts to spaced segments uses a distributer to provide the appropriate delay, Fig. 6 (not shown). In a further arrangement, Fig. 7 (not shown), in which any five signal elements can be regarded as represented by the combination of three co-ordinates each of which can have two conditions, as described in Specification 652,601, the delay is determined by three distributers having segments differently connected to two contacts operated by three relays representing the three co-ordinates. Other arrangements, Fig. 10, 11 (not shown), are based on the assumption that the delays for a signal combination are approximately equal to the sum of the delays which can be associated with component values allocated to the individual co-ordinates representative of the combination. A further embodiment, Figs. 14a, 14b (not shown), arranged for the precorrection of bivalent signals is dependent on the analytical representation of any five signal elements by a combination of four parameters each of which may have one of three conditions, and the assumption that the delay appertaining to any combination is approximately equal to the sum of delays associated with the respective conditions of the four parameters. The embodiment also employs the arrangement by which a trivalent modulation is effectively represented by two component divalent modulations, as described in Specification 668,272.