Epson 8900 Series - Manual (Page 208)

Communication Interfaces 10-17
Clear to Send Signal
The host computer generates the clear to send (CTS) signal to
indicate that it can receive data from the printer. In the DIRECT
CONNECT mode, the printer ignores this signal. In the MODEM
CONNECT mode, CTS must be on for the printer to send data. If
the interface cable does not provide a connection to this pin, the
printer holds CTS in its on state.
Data Set Ready Signal
The host activates the data set ready (DSR) signal to enable the
printer to send and receive data. If the interface cable does not
provide a connection to this pin, the printer holds DSR in its active
state.
Data Carrier Detect Signal
The host activates the data carrier detect (DCD) signal to enable the
printer to send data when operating in the MODEM CONNECT
mode. When the printer is in the DIRECT CONNECT mode, it
ignores this signal. If the interface cable does not provide a connection
to this pin, the printer holds DCD in its on state.
Data Terminal Ready Signal
If the PIN 20 H:READY (pin 20 high on ready) parameter was
selected during printer setup and the printer is operating in the
DIRECT CONNECT mode, the printer activates DTR to indicate
that it is ready to receive data and deactivates DTR to indicate that it
is busy. Otherwise, the printer activates DTR following self-test
completion at power-up to indicate that it is online and ready to
receive data.