Automatic Fall-Back Mode - OKIDATA OF1000 Service Manual

Page: 17
Service Guide OF1000
Chapter 2 Principles of Operation

2.1.04 Automatic Fall-back Mode

The Okifax 1000 will change the message transmitting speed according to the following fall-back
plan. The Okifax 1000 will first transmit a page of the message at 9600 bps. The receiving station
will continuously monitor the received data. If the receiving station detects six or more consecutive
error lines during reception of a single page, or if the total number of errors detected during the
reception of a single page exceeds 10% of the data on the transmitted page, it will return an RTN
(Retrain Negative) signal to the transmitting station upon termination of the page reception. With
an RTN signal received, the transmitting station will downgrade its speed by one level (to 7200
bps in this case) and continue transmission of the next page. Similarly, should the transmitting
station again receive an RTN signal from the receiving station, it will downgrade speed another
level.
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