Assume that one of the operators in your station reports that a teletypewriter is "running open." This means that
the teletypewriter is receiving a steady:
mark signal--it does not perform any operations.
mark signal--it suddenly stops in the middle of a message.
space signal--it performs mechanical operations but does not print.
mark and space signal in alternation--it prints a garbled message.
The advantages gained by using neutral signals instead of polar signals in dc teletypewriter circuits are:
circuits are less expensive and they are easier to install.
circuits are easier to install and the signals can be transmitted over greater distances.
Signals can be transmitted over greater distances and they are not readily affected by inductance and
signals are not readily affected by inductance and capacitance in circuits, and the line power loss is less.
Assume that you are tracing the current path on the schematic diagram of a dull-duplex teletypewriter circuit.
What symbol would you look for to locate the voltage source?