Sage data terminals

In the sage (semiautomatic ground environment) System,1,2 the function of converting the data in the form generated or used by the processing equipment to a form suitable for transmission over the communication channel is performed by the terminal apparatus of the Western Electric Al digital data signaling system. The major components of the terminals, as shown in the simplified diagram of Fig. 1, are the digital data transmitter (DDT) and the digital data receiver (DDR). At the originating terminal, the data source furnishes three separate components of information to the transmitter: timing, data, and start. The timing component is a continuous sine wave of either 1,300 or 1,600 cps (cycles per second), depending upon the bit rate, which provides means for synchronizing the system. Message information, contained in the data component, is in the form of dipulses. (A dipulse is one complete cycle of the timing wave per bit, which, in telegraph terminology, represents a mark. Absence of a dipulse in the data component represents a space.) The start component consists of single dipulses which group the data into words.