Polarential telegraph system
Two types of polarential systems, known as types A and B, are in use. In half-duplex operation of a type A polarential system, the direct-current balance is independent of line resistance. In half-duplex operation of a type B polarential system, the direct current is substantially independent of the line leakage. Type A is better for cable loops where leakage is negligible but resistance varies with temperature. Type B is considered better for open wire where variable line leakage is frequent.
- Frank Jay (1977). IEEE Standard Dictionary of Electrical and Electronics Terms. p. 501. "A direct-current telegraph system employing polar transmission in one direction and a form of differential duplex..."
- This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C" (in support of MIL-STD-188).