Transmit-receive circuit for electronic teleprinter - uses two transistors to give same behaviour as electromechanical teleprinter

摘要

The transmit/receive circuit matches an electronic teleprinter to the circuits of a telephone exchange so that as far as the exchange is concerned it behaves as an ordinary electromechanical teleprinter. Two transistors each with collector resistors are capacitively coupled together by their collectors. The collector of the second transistor is connected over a diode to the base of the first and both transistors are coupled to receive logic and to the transmit logic, and over two terminals to the telegraphic lines. Inductance is simulated slowly turning on the first transistor controlled by the capacitor and thereby causing the current in the telegraphic lines to rise at a pre-determined rate.