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Chapter 1 - Introduction
1.8 Modem LED Indicators
The MT2834MR6 has five LED indicators per modem:
TD Transmit Data. This LED blinks when data is being transmitted, on for a space, off for a mark. The
state of this LED matches that of the TD circuit on Pin 2 of the RS-232C interface.
RD Receive Data. This LED blinks when data is received, on for a space, off for a mark. The state of
this LED matches that of the RD circuit on Pin 3 of the RS-232C interface.
CD Carrier On. This LED lights when a valid carrier tone has been detected.
Speed Speed. This LED blinks at different rates to indicate the speed of the data connection:
Data Rate (bps) LED State
12000 or less Off
14400 or 16800 Slow blink rate
19200 or 21600 Medium blink rate
24000 or 26400 Fast blink rate
28800 or more On
OH/OOS Off Hook/Out of Service. This LED lights when the modem is off hook, which occurs when the
modem is dialing, online, or answering a call. The LED flashes when the modem is in the busy-
out or out-of-service state.

Note: The PS4800 modem rack power supply has one LED that indicates the presence of all supply voltages.

1.9 Busy Switch
The MT2834MR6 has six two-position Busy switches on the front panel. Each switch can be used to create a
“busy-out” (OOS) condition for one of the six on-board modems (i.e., modem A, B, C, D, E, or F).
To place a modem in the Busy condition, move the appropriate Busy switch to the right. The selected modem
goes off-hook, its OH/OOS LED begins to flash, and incoming calls to this modem get a busy signal. If you
suspect a problem with a particular modem, you can use the Busy switch to have an optional device (such as
a “hunt group”) that looks for a non-busy line to perform a rollover to the next available modem while you
check the status of the Busy modem.

Note: The MultiModemManager can perform the same function using software.