TM 11-5805-246-10
Section Ill TECHNICAL PRINCIPLES OF OPERATION
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Subject
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Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Component Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-12. OPERATING CHARACTERISTICS.
Telegraph Terminals TH-5/TG and TH-5A/TG are used between teletypewriter stations to provide
teletypewriter transmission over lines which will not pass direct current (de). For transmitting, the
neutral mark and space signals from the teletypewriter are 1,325 and 1,225 Hz respectively. The
received voice frequency (vf) signals are changed back to the corresponding neutral dc signals. The
telegraph terminal provides a means of 20 Hz signaling. If vf signaling is needed a vf ringer such as
Telegraph-Telephone Signal Converter TA-182/U must be used. The telegraph terminal also provides for
connection of a local-battery field telephone. Teletypewriter transmissions cannot be made when the
telephone is in use.
1-13. COMPONENT FUNCTIONS.
Component functions are divided into the following groups:
Sending circuit: Changes neutral dc teletypewriter signals to vf frequency shift teletypewriter
signals.
Carrier removal circuit: Prevents the output of the sending circuit from being applied to the
line when the teletypewriter sends a consent mark (idle) signal.
Receiving circuit: Changes vf frequency shift teletypewriter signals to neutral dc tele-
typewriter signals.
Threshold circuit (level control): Disables the receiving circuit when vf frequency shift
teletypewriter signals below approximately 50 dbm are received from the line.
Signaling and ringing circuits: Transmit and receive 20 Hz signals.
Power supply: Provides operating power for the circuits of the telegraph terminal.
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