GB1268462A - Data transmission system - Google Patents

Abstract

1,268,462. Digital transmission systems. INTERNATIONAL BUSINESS MACHINES CORP. 14 April, 1970 [14 April, 1969], No. 17777/70. Heading H4P. In a data transmission system wherein each primary digit is represented by a sequence S comprising a main signal pulse and a predetermined number of preceding and following echo pulses at determined intervals, for each sequence, a series S<SP>1</SP> is generated comprising symmetrical pulses of the form which is summed with the corresponding sequence S and passed through a low pass filter producing a signal, to be transmitted, of a form capable of being demodulated in a conventional device operating at the data repetition rate Ts. The transmitter includes a generator of elementary signals representing data elements, which are received by a register having a number of positions determined by the number of weighted pulses and/or time duration of each signal, a means for generating the series S<SP>1</SP>, and an analogue adder under the control of clock signals which produces a corresponding signal amplitude in respect the values obtaining at the input and/or the positions in the register. Alternate signals may be inverted. The transmitted signal is substantially identical to a frequency modulated signal which may be received by a conventional f.m. demodulating device. Sequences A, B of main and echo signals S representative of individual data elements are shown in the upper two lines of Fig. 1, B being shown inverted and the value of each element being represented by the amplitude. A signal of the form S<SP>1</SP> is generated for each group, that for A being shown in line 6 which signals have an amplitude of 0À707 A max. Each group of signals S<SP>1</SP> is added to the corresponding group S in an analogue adder which after passing through a low pass filter gives a signal of digital type which may be transmitted and which is substantially identical to a f.m. signal. Arrangements for generating and combining the signals are described in the Specification.