Twinning allows calls to a user main extension number to alert at both that extension and a secondary extension. This feature is aimed primarily at users who have both a desk phone and a wireless extension. Calls from the secondary twinned extension are presented as if from the user's main extension. Presentation of call waiting and busy is based on whether either of the twinned extensions is in use.

When a call is presented to the primary phone the secondary will ring. If the primary phone does not ring, for example in Do Not Disturb, the secondary phone will not ring.

This is typically used in scenarios like workshops or warehouses where team supervisors may have a desk with a fixed phone but also have a wireless extension (e.g. DECT). When a call is made from either twinned phone, the call will appear to have come from the primary phone. Other users of the system need not know that the supervisor has two different phones. The supervisor’s Coverage Timer and No Answer Time are started for the call and if the call is not answered within that time, the call will be delivered to available coverage buttons and then voicemail.

The following features are supported with twinning:

• Follow Me To
• Follow Me Here
• Forwarding
• Do Not Disturb (including exceptions)
• Context less hunt group actions: Membership/Service Status/Fallback Group configuration
• Voicemail On/Off/Access
• Call Log (Central Call Log 1600 phones only)
• Redial (Central Call Log 1600 phones only)
• Personal Directory Entries (for 1600 phones only)

Mobility features include:

• Mobile (external) Twinning
• Mobile Call Control
• Mobility Callback