Siemens SIMATIC NET SINAUT ST7 System Manual page 269

Table 6-23
LED no.
1
2
3
4
5
6
The RTS and CTS signal names are irrelevant for the MD3.
The following table summarizes the meaning and activity of the six LEDs on the front of the
modem for dedicated line operation.
SINAUT ST7 Station control system - System Manual
System Manual, 05/2007, C79000-G8976-C178-06
Meaning of the LEDs on the front of the MD3 for dial-up operation
Labeling Description
TXD Transmit data
The LED flashes in rhythm with the data flow sent to the modem by the
terminal device (TIM) over the RS-232 or RS-485 interface.
RXD Receive data
The LED flashes in rhythm with the data flow sent by the modem to the
terminal device (TIM) over the RS-232 or RS-485 interface. The data
flow is indicated both in the data and in the command phase.
DTR Data terminal ready
Outgoing call:
The LED lights up when the terminal device (TIM) wants to establish a
connection and goes off as soon as the terminal device wants to
terminate the established connection. If no connection can be
established or the connection is terminated by the partner or is aborted
due to a disruption, the terminal device deactivates the DTR signal as
soon as it receives a message to this effect from the modem.
Incoming call:
The LED lights up when the terminal device (TIM) wants to accept an
incoming call. The LED goes off again under the same conditions as
with an outgoing call.
RTS / ONL Modem online (ONL) "receiver taken off the hook"
Outgoing call:
The LED lights up as soon as the modem has received the dialing
command from the terminal device (TIM) and begins connection
establishment. The LED goes off again when the connection is
terminated (by its own terminal device or by the partner) or when the
connection is aborted due to a disruption.
Incoming call:
The LED lights up when the terminal device (TIM) signals with DTR that
it wants to accept the incoming call. The LED goes off again under the
same conditions as with an outgoing call.
CTS / RI Ring indicator (RI)
The LED lights up when there is an incoming call.
DCD The LED has a dual function:
1. Operating status
This signals the operating status of the modem. The LED lights up after
the power is turned on if the operating voltage is correct. If the modem
is not operational, the LED remains off.
2. Connection established
During normal operation of the modem, the LED goes off as soon as
the two participating modems are synchronized during connection
establishment (reported to terminal device with CONNECT). The LED
lights up again when the connection is terminated or aborted due to a
disruption.
Installing and putting a SINAUT modem into operation
6.6 Analog dial-up modem MD3
269