Multiple digital telegraphic data channels in one speech channel - employing time multiplexing and use of single digital transmitters and receivers

摘要

The application is to telegraphic alternating current digital signal transmission. The object is to require less equipment in order to achieve the necessary encoding and decoding. A single transmitter and receiver are used with time division multiplexing and digital filtering based on the algorithm of the fast Fourier transform. In a typical receiver, the incoming analog signal is applied to a low pass filter and then converted into a digital signal. In the following stage the digital filtering is carried out, and subsequently the individual channels formed by the time division multiplexing circuit. The transmitter unit operates in a similar manner but in reverse order.