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Modem

Modem. acronym for mo dulator- dem odulator converts a series of binary voltage pulses into an analog signal the receiving modem translates the analog signal back into digital data. Date Flow: Simplex. only transmit in one direction. One way. Monitor. Computer. Data Flow: Half Duplex.

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Modem

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  1. Modem • acronym for modulator-demodulator • converts a series of binary voltage pulses into an analog signal • the receiving modem translates the analog signal back into digital data

  2. Date Flow: Simplex • only transmit in one direction One way Monitor Computer

  3. Data Flow: Half Duplex • data may travel in both directions, but only in one direction at a time • non-simultaneous two-way communication • computers use control signals to negotiate when to send and when to receive

  4. Half Duplex

  5. Data Flow: Full Duplex • complete two-way simultaneous transmission • faster than half-duplex communication because no turnaround time is needed

  6. Used for connections between computer and modems, among other things 25-pin connector with a specific arrangement of leads computer usually has male DB25 connectors while modems are female In practice, fewer than 25 wires are generally used in applications RS-232C

  7. DB-25 Female DB-25 Male RS-232 DB-25 Connectors

  8. RS-232 DB-25 Pinouts

  9. Limited RS-232 RS-232 DB-9 Connectors

  10. MODEM COMMANDSMEMORIZE THESE! • AT- PROCEDES ALL MODEM COMMANDS • ATDT- DIAL PHONE # USING TOUCH TONE • ATDP- DIAL PHONE # USING PULSE DIALING • ATA- ANSWER AN INCOMING CALL • ATHO- HANG UP IMMEDIATELY • AT&F- RESET MODEM TO FACTORY SETTING • ATZ- RESET TO POWER UP SETTINGS • *70- CANCEL CALL WAITING

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