Furuno MULTI-COMMUNICATION UNIT IB-782 - Manual (Page 13)

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1.7 Receive-Only Telephone
Any telephone connected to the IB-782 can be designated as a “receive-only telephone.”
This requires setting of a DIP switch. For this procedure see paragraph 2.3.
Setting
From the telephone to set as “receive only”, dial [*], [5], [9], [1], [#]
Cancelling
From the telephone not designated as receive-only telephone, dial [*], [5], [9], [1] and the
telephone number you wish to cancel as a receive-only telephone.
Note:
The intercom function is not available from a “receive-only telephone.”