FIGURE 89. Simplexed Teletypewriter
Circuit, Phantom Telephone
Important Points to Remember.
a. In a half-duplex circuit, if both stations are transmitting at the same time, the printed copy would be garbled
because each teletypewriter would try to print both home copy and receive copy at the same time.
b. Current adjust potentiometers allow the current to be adjusted to a predetermined value.
c. Full-metallic circuits are always used for classified messages.
d. You need twice as many line wires or cables in a full-duplex circuit.
e. The two windings on a polar relay are called the line winding and the bias winding.
f. DC teletypewriter circuits can use existing telephone circuits to interconnect the transmitting and receiving
stations; thus, the installation of line wires or cables is unnecessary.