GB1391631A - Transmitter for a data transmission system employing a multi-level code - Google Patents

Abstract

1391631 Digital transmission; multi-level signals SOC ITALIANA TELECOMUNICAZIONI SIEMENS SpA 14 March 1972 [21 Sept 1971] 11757/72 Heading H4P A transmitter producing a multi-level signal transmittable in voice frequency band comprises a converter S/P dividing a binary message I into odd and even bits II, III each of double length of the original which are applied to a coder COD transforming them into six parallel two-level signals which are converted at D/A into a six-level signal, according to table 2 (not shown), given in the Specification, delayed by two bits at R. This is subtracted at Z from the undelayed signal providing a 7-level output which modulator M translates from 0-2400 Hz band to 600-3000 Hz band for transmission on a telephone line. At the receiver this is translated back to 0-2400 Hz band and a rectifier L inverts negative values and supplies a 4-level signal equal to the sum of signals II, III which are decoded at E producing a replica of I. Coder COD comprises an arrangement of logic gates described in connection with Fig. 2 (not shown), the operation being that if numbers 0-3 represent the four possible combinations of input and 0-5 the six outputs, the output which is active in response to an incoming nth bit is different in its position from the output activated in response to the (n-k)th bit by a number equal to the combination number of the incoming information. In table 2 (not shown), k=2.