Modems

Prologic Recruitment Ltd Training Division

A+ Part I Computer Hardware

MODEMS

Mathew Abraham Prologic Recruitment Ltd.

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Modems    

Overview Terminology Operation Troubleshooting

Prologic Recruitment Ltd.

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Overview  

Modulation Demodulation

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Two Main Types 

External Serial Cable (RS-232C)

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Internal Prologic Recruitment Ltd.

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External Modem

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INTERNAL MODEM 

PCI

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ISA

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TERMINOLOGY 

Modem - Modulation/demodulation

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DTE/DCE – Data terminal equipment/Data communication Equipment

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UART – Universal asynchronous receiver/transmitter- serves many purposes governing communication over serial ports including converting signals from parallel to serial

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Full duplex – being able to send and receive information at the same time

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Half duplex – Like a information can be send or received at any given time Prologic Recruitment Ltd.

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DTE/DCE

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Half Duplex

Sending or receiving only one at a time Prologic Recruitment Ltd.

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Full Duplex

Sends and receives at the same time Prologic Recruitment Ltd.

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Speed 

BAUD – Number of times/second a signal changes the state.

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BPS – Bits/sec

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Modem Standards

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Handshaking   

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Calling modem dials a number Answering modem picks up and issues a carrier tone. Answering machine sends different carrier signals until calling machine responds. They agree upon carrier speed, compression, etc. Establish Communication session Prologic Recruitment Ltd.

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Handshaking

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Troubleshooting 

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Modem plugged in, turned on? (external) Modem seated in slot properly (internal) Make sure comport and IRQ and I/O addresses are set correctly. Proper driver installed?

Prologic Recruitment Ltd.

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