Simultaneous transmission of voice and digital data signals via telecommunications network, using operational amplifiers and delay circuits to convert digital signals to analogue version

摘要

The digital signal input (12) is in bytes each of which has a number of bits. The most significant bit is converted to an analogue pulse with an amplitude which is larger than the next most significant bit, and so on. Each bit in a byte is delayed by a preset time, so that its sequential position indicates its significance. At the other end of the transmission network, sum and difference circuits are used to regenerate the data.