Modem LEDs
The information in this section applies to Hayes external modems.
AA - Auto Answer
AA indicates the states of S-register S0
and the ringer detector system. If S0=0, AA will be OFF while the absence
of a ringer signal is detected, and AA will be ON while a valid ringer signal
is being detected. If S0>0, AA is ON when no ring signal is detected,
and AA is OFF while a valid ringer signal has been detected.
CD - Carrier Detection
CD indicates the state of the modem carrier detector system. CD is off
in the idle state. In the handshaking state, CD comes on after the CONNECT
result code is sent to the DTE. Once the online state is entered, CD tracks
detected carrier within 20 ms (LED ON means carrier power detected).
CD is not affected by the value of S9 - Carrier Recovery
Time or the &Cn command. Refer to Handshaking
State.
HS - High Speed
HS and the HS leads of the DTE interface (pins 12 and 23) indicate the
same state. In the online command or idle states, HS is ON when the AT speed
is greater than or equal to 4800 bits/s, and is off otherwise. In the online
state, HS is ON when the line speed is greater than or equal to 4800 bits/s,
and is OFF otherwise. In the handshaking state, HS may change after the
CONNECT result code is sent to the DTE.
MR - Modem Ready
MR indicates if a power up test fails or if a self test is currently
active. On power up, if the RAM read/write test fails, MR goes OFF and the
modem stops further activity. If RAM passes but the computed PROM checksum
is incorrect, MR attempts to flash at a rate of 853 ms ON, 853 ms OFF (+10%)
while preventing additional activity. If both tests pass, MR remains ON.
When a self test (&T1, &T3,
&T6-&T8) is
running, MR also flashes at the above rate until the test is terminated
and while the Remote Digital Loopback (RDL) process is operating.
OH - Off Hook
OH shows the state of the line relay. OH is off while the modem is on
hook.
RD - Receive Data
RD represents the serial data sent to the DTE from the modem over the
RD line (pin 3). RD is off when the signal represents a mark.
SD - Send Data
SD represents the serial data sent to the modem from the DTE over the
TD line (pin 2). SD tracks the signal on Pin 2 of the DTE interface within
1 ms. A mark signal on Pin 2 corresponds to the LED being off and SD is
off when the DTE is not sending characters to the modem.
TR - Terminal Ready
TR indicates the state of the DTR line (pin 20). If &Q0
and &D0 are in effect, TR remains on regardless
of the state of DTR. Otherwise, TR tracks the state of DTR. In the idle
state or online command state, TR tracks DTR within 50 ms. While in the
online state, tracking is within 10 ms.
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