Honeywell KLN 900s Pilot's Manual page 185

If while this message is being displayed on the slave KLN
900, the master begins to respond, tandem operation will
resume. If the ENT button is pressed while this message
is displayed on the slave KLN 900, it will reinitialize for
stand alone operation. (Note for the slave to operate in
stand alone mode, it needs to be equipped with its own
database and antenna.) While the Slave is operating
stand alone, the message "OTHER KLN 900 NOT
RESPONDING" will be displayed on the slave's message
page. Should the power be cycled on the slave unit, the
normal power up sequence is followed and the slave KLN
900 will re-attempt tandem operation.
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