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