Epson Equity II - Manual (Page 129)

When you select option 11 from the DEVICE LIST, you see these
prompts:
Attach loop-back connector to serial port.
Enter Y to start this check when connector is
attached, or
Enter N to return to the menu.
Insert the loop-back connector. Then press Y and Enter to start the check.
First, the computer checks the serial port control lines to see that they
are able to change from high to low and vice versa. No messages display
during this part of the test unless an error occurs.
The second test is an echo back check during which the port sends data
to itself in a fixed data format, at all the possible baud rates. When this test
begins, you see these messages:
RS232C echo back check - at various baud rates
Current baud rate is 75
Current test data is 00
Each baud rate is tested in turn, and the display informs you of the
progress of the test. If the port does not become ready correctly, a timeout
error occurs. If any data received does not match the data sent, a verify error
occurs, and the computer reports the transmitted and received data at the
time of the error.
The final test is an echo back check during which the port sends data to
itself at 9600 baud, using various data formats. At the start of the test, you
see these messages:
RS232C
echo back check - with various data formats
Current data format: 5 data bits, 1 stop bits,
parity - NONE
Current test data is 00
Once again, if any data received does not match the data sent, a verify
error occurs, and the computer reports the transmitted and received data at
the time of the error.
4-22 Diagnostics