atcomsystems.ca/forum Forums TDM Business Telephone Systems Nortel Telephones & Systems Distinctive Ring

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From the manual 7.1:
If the ring type is changed on a telephone after the DRPs are
set on the line, the line DRPs are overwritten by the telephone
settings.
If the line DRPs are set after telephone programming, then the
telephone ring programming is overridden by the DRP. Refer
to the Modular ICS System Administrator Guide for details
about setting ring types on a telephone.
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However if the number is being used under a Line it wont let you choose it in F*7 anyway.