Learning by Doing: CISCO Certified Network ... - SCN Research

AT&F load factory defaults and settings
S0=1 set modem to answer on first ring
&C1&D3 set modem up for “action” (cd/dtr)
&K3 set hardware flow control
&Q9 set compression
&W save configuration to modem
During the course of using modems there are several other “abbreviations” you should
also be familiar with. You will see these when using modems with routers and using the
“debug” commands:
TxD transmit data DSR Data Set Ready
RxD receive data GRD Signal ground
RTS request to send CD Carrier detect
CTS clear to send DTR Data terminal ready
You have also seen “blinking lights” on an external modem (if you used the external
type). On my Hayes here is what those lights mean:
HS High-speed Lights when communicating at more than 4800kbps
RI Ring Indicate Blinks on and off when detecting incoming ring
CD Carrier Detect Lights when the DCD signal from the fax modem to
the computer is on
OH Off Hook Lights when the fax modem is off hook
RD Receive Data Light flashes when data is sent from the fax modem
to your computer or other serial device. At high speeds the light may appear to be
always “on.”
SD Send Data Flashes whenever data or commands are transmitted
from the serial port of your computer or other device to the fax modem.
TR Terminal Ready Lights when the computer is ready to send or
receive data. Indicates the status of the DTR signal from the terminal or
computer.
MR Modem Ready Lights when the fax modem is turned on. Flashes
during self-test.
Above information from “Hayes Installation Guide” (2000).
Step-By-Step Instructions:
1. Set up the lab and cable it as shown.
2. Have each computer, one at a time, establish DUN between each other. Be
sure to watch the indicator lights on the modem. Try to record the order
during a call establishment and termination.
3. Try calling from one phone to another.
4. Try calling from one phone into another computer. As it tries to go you will
hear negotiation taking place (Screech! Squak! Scratch!)
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