Epson 1000 Reference Manual page 174

Signal
Pin
4
5
6
8
20
A-14 Technical Specifications
Signal Direction
RTS OUT
IN
CTS
DSR IN
SG
IN
DCD
DTR OUT
Description
Request to send. This pin is held
high by the printer.
Clear to send. This pin indicates
that the computer is ready to
receive data from the printer. The
printer will not proceed unless the
signal is high. Can be set high with
SelecType.
Data set ready. This pin indicates
that the computer is ready to
receive data from the printer. Can
be set high with SelecType.
Signal ground. This pin provides a
ground for all the signal lines.
Data carrier detect. Always
ignored.
Data terminal ready. This pin
indicates whether or not the printer
is ready to receive data. If the
printer ready protocol is not
selected, this pin is always high
(i.e. the printer is ready to receive
data). If printer ready protocol is
selected, the printer can accept
data when the pin level is high, and
cannot accept data when the pin
level is low. When the DTR signal
goes low the host computer must
stop sending data within 128
characters. Can be set high or low
with SelecType.