An electronic teleprinter distributor

MOST of the extensively used teleprinters of today have mechanically operated cam-type distributors. Although these are quite satisfactory and reliable, a recent trend in the industry has been to develop electronic distributors. A distributor of this type has been developed at the Electrical Engineering Laboratory of the University of Roorkee, India. It uses eight cold-cathode thyratrons or trigger tubes connected as a ring counter. One of the tubes keeps glowing and maintains marking current in the line when the transmitter is idle. When a character is transmitted, the tubes fire one after another in a serial sequence. The timing pulses are derived from the 50-cycle mains supply. Although any fluctuation of the supply frequency will affect the output waveform, it has been seen that if the frequency variation is limited to 4%, a teleprinter receiver having a margin of 35% will function properly.