Solution:
Trueport in Standard Mode has two types of devices; ttys and ttyS. The ttys is a terminal device and ttyS is a modem device.
The modem device monitors DCD. If DCD is low the device is disabled. If DCD is high the device is available. If a process such as getty is applied to the ttyS device it will not start until DCD is high.
If DCD drops then the host will send a signal hangup to all processes running against the device. This simulates the same process that a local COM port can produce. When the signal hangup occurs a process such as getty will be respawned.
You will have to ensure that the cable supports RTS and DCD signalling. Normally you can tie DCD to DTR on the cable, so when DTR drops (such as the terminal is turned off) DCD will drop also.
The host will use the ttyS device instead of the ttys device.
Example pin diagram for a dumb terminal modem device control:
Modem device cable example for a dumb terminal
RJ45 DB25 Terminal
DCD 1 ------------------- 20 DTR
S/GND 4 ------------------- 7 S/GND
TXD 5 ------------------- 3 RXD
RXD 6 ------------------- 2 TXD
RTS 8 ------------------- 4 RTS