Oki Microline 520 Service Handbook page 248

RAP 11 Serial Interface Problem
START.
Are you using a cable with the proper number of pins?
No Change the interface cable.
Has the problem been resolved?
Yes End of procedure
No Go to A
Yes Is the ALARM LED blinking?
Yes Refer to Section 4.6 of the Service Handbook.
Has the problem been resolved?
Yes End of procedure
No Go to A
No Go to A
A
Check the serial interface parameters for the RS232C (in the Printer Menu): baud rate,
word length, parity, protocol, busy signal and parity.
Has the problem been resolved?
Yes End of procedure
No Go to B
Failure Analysis 4 - 40 Microline 520/521 Service Handbook
P/N 59257803