Siemens SINAUT ST7 System Manual page 194

Installing and putting a SINAUT modem into operation
5.5 MD2 dedicated line modem
LED displays of the MD2
The following table summarizes the meaning and activity of the six green LEDs on the front
of the modem.
Table 5- 9
LED no.
1
2
3
4
5
6
194
Meaning and activity of the LEDs on the front of the MD2
Labeling Description
TXD Transmit data
The LED flashes in rhythm with the data flow sent to the modem and to
the WAN interface by the terminal device (for example TIM) over the RS-
232 or RS-485 interface.
RXD Receive data
The LED flashes in rhythm with the data flow received by the modem
over the WAN interface and transferred to the terminal device (for
example TIM) over the RS-232 or RS-485 interface.
DTR Data terminal ready
Indicates the status of the DTR signal of the connected terminal (for
example TIM). As soon as a terminal device has started up, it sets its
DTR signal to 1 after which the "DTR" LED on the MD2 is lit continuously.
RTS Request to send (RTS)
Indicates the status of the RTS signal of the connected terminal (for
example TIM). When a terminal device turns on the transmitter of the
modem, it sets its RTS signal to 1. As long as RTS is set to 1, the "RTS"
LED is lit on the MD2. The LED goes off as soon as the terminal device
deactivates the RTS signal.
CTS Clear to send (CTS)
When the transmitter of the modem has been turned on by RTS, the
modem signals back to the terminal device (for example TIM) that it is
clear to send by setting its CTS signal to 1. As long as CTS is set to 1,
the "CTS" LED on the MD2 modem is lit. The LED goes off as soon as
the terminal device deactivates the RTS signal and turns off the
transmitter of the modem.
DCD/5V Data carrier detect
The "DCD" LED lights up as soon as the internal operating voltage of the
MD2 modem is applied.
Whenever the MD2 detects an adequate receive level on its receive
channel, the "DCD" LED goes off.
System Manual, 07/2009, C79000-G8976-C178-07
Station control system