Programming Manual References
7.1  [5-1] Doorphone
Feature Guide References
1.17.2  Door Open
External Relay Access
Specifies the feature number used to activate a relay.
Value Range
Max. 4 digits (consisting of 0–9, *, and #)
Maintenance Console Location
4.9  [2-6-1] Numbering Plan
—Main
Programming Manual References
7.6  [5-4] External Relay
Feature Guide References
1.17.10  External Relay Control
External Feature Access
Specifies the feature number used to access the features of a host PBX or the telephone company.
Value Range
Max. 4 digits (consisting of 0–9, *, and #)
Maintenance Console Location
4.9  [2-6-1] Numbering Plan
—Main
Programming Manual References
None
Feature Guide References
1.11.7  External Feature Access (EFA)
ISDN Hold
Specifies 
the feature number used to hold a call using the ISDN service of the telephone company, instead of
the PBX feature.
508 PC Programming Manual
4.9 [2-6-1] Numbering Plan—Main