Abstract :
A description is given of the principles of operation of a pulse-modulated radio-telephone system intended for ground point-to-point use and providing up to twelve simultaneous channels of two-way telephone communication. Each channel is capable of accommodating up to four channels of teleprinter signals as an alternative to speech. The operating frequency band is from 450 to 500 Mc/s, and directional aerials having a beam width of approximately ±15° are used. All the pulses are of equal amplitude and duration, the intelligence from each channel being separately conveyed by successive pulses whose positions in time relative to a set of marker signals are varied in accordance with the voltage from the associated channel signal. The marker signal consists of a regularly recurrent group of three equally-spaced pulses each identical with the channel pulses. The transmitter power of approximately 200 watts peak is sufficient to permit working over line-of-sight paths up to 100 miles long. The necessary arrangements, including ringing facilities, are provided for connection to two- or four-wire landlines, and a self-contained two-channel-unit construction economizes in equipment when the number of channels required is less than the maximum.
