FIGURE 1-2. MODEM: TYPICAL CONFIGURATION FOR DUPLEX LANDLINE (600 OHMS) TELETYPEWRITER SYSTEM

TM 11-5805-387-20-2

FIGURE 1-2. MODEM: TYPICAL CONFIGURATION FOR DUPLEX LANDLINE (600 OHMS)

TELETYPEWRITER SYSTEM

1 Teletypewriter [tty (SEND)] dc mark and space pulses are sensed by the modem.

2 Voice signals from the microphone are routed through the modem for switching purposes.

3 The modem converts the tty SEND mark and space pulses to tty tones.

4 These tones and voice signals are applied to an isolation amplifier, which provides impedance

matching for transmission over telephone lines to a distant station.

5 When received, an isolation amplifier again provides impedance matching. The received signals

are applied to the modem. The tty tones are converted into tty dc puIses.

6 The tty pulses are applied to a teletypewriter [tty (RCV)] and applied to page printers or tape

punches for message interpretation.

7 An audio output can be applied to a speaker for local use.

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