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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
SINAUT ST7 station control system
System Manual, 09/2016, C79000-G8976-C178-10
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 exam-
ple 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 ex-
ample 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 ex-
ample TIM). When a terminal device turns on the transmitter of the mo-
dem, 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 transmit-
ter 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.
Installation and commissioning of the modems and routers
5.5 MD2 dedicated line modem
155
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