Panasonic KX-TVS120 Installation Manual page 59

Signal Ground (SG)
Connects to the DC ground of the unit for all interface signals.
Data Terminal Ready (DTR)—output
This signal line is turned on by the unit to indicate that it is RS-232C on-line. Circuit DTR ON
does not indicate that communication has been established with the terminal/printer. It is
switched off when the unit is RS-232C off-line.
Installation Manual
INSTALLATION
59