GB1059150A - Improvements relating to arrangements for the transmission of communication signals by pulse code modulation transmission - Google Patents

Abstract

1,059,150. Pulse code modulation. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Oct. 18, 1965 [Oct. 27, 1964], No. 43766/64. Heading G4H. [Also in Division H4] In the system for transmitting signals such as speech signals in pulse form the coder at the sending end samples the input and transforms it into a series of digits the first of which indicates the sign, the next two the amplification factor and the remainder the value. In the form shown speech input signals on a plurality of input lines are sampled sequentially and each sampled signal transmitted via lines L1, L2 (Fig. 1A, not shown) to an addition circuit and polarity indicator, the output from the latter being on one of two lines P1, P2 depending on whether the signal is positive or negative. If for example the signal appearing on line L2 is 2000 volts, the first input pulse at terminal T3 (Fig. 1B, not shown) to a digit ring transmits a pulse via terminal D1B to the transmission path TP to indicate that data is going to be transmitted. During the remaining seven digit intervals gates G8-G22 are selectively enabled by the output from the polarity indicator and the pulses appearing at terminals T3 and T4 to set or reset bi-stable triggers M1- N11 resulting in a pulse train 1011100 being transmitted to the pulse sending circuit and also resulting in the enabling of selected ones of the gates C1-G4 to enable switches S1-S4 to pass currents from the fixed value current producing elements, the switches multiplying the produced current by a fixed amount. The output from the switches is fed to an attenuator unit which feeds a signal of the corresponding voltage to the addition circuit AC for comparison with the sampled input during each digit interval. At the receiver (Figs. 2A, 2B, not shown) during the first digit interval a pulse arrives at terminal T10 to indicate the arrival of data. The following seven bits control gates GB5- GB16 and consequently control the setting of bi-stable triggers BM1, BM2 enabling gates GB1-GB4 controlling current switching means BS1-BS4 and bi-stable triggers BM3-BM8 which control fixed value current producing elements to determine the current that shall pass through the switching means. In an attenuator the output from the switches is combined to produce a voltage on line L5 corresponding to the input voltage at the transmitter. This voltage is fed to distributing and demodulating circuits, the outputs from which are speech signals on a plurality of lines.