Transmit coupler for binary data - has transformer and resistors chosen for same output impedance for both logic states

摘要

The transmit coupler, for data, couples pseudo-ternary data signals to a transmission line using a cheaper transformer and a better matching than similar types. The coupler also has fewer components and a broad frequency range. The transformer (tr11) is connected between the transmission line (a, b) and the two earthed switches (S) whose operation denote the 0 and 1 states. The transformer primary is shunted by a first resistor (R12) and by two series resistors (R10, R11). The junction between the series resistors is coupled to the positive supply pole. The transfer ratio and resistors are chosen to make the output impedance the same for both states.