Using this feature, a CTI application can control extending of calls to Single and Dual mode applications: EC500, CSP, SPFMC, PBFMC, and PVFMC. If multiple applications are administered for an endpoint, the desk set applies the MCE only to the supported applications. The feature is invoked by making the office telephone call the Mobile Call Extension. This causes a call to be initiated to the phone number of the application. This extension is administered on the Off-Pbx Mobile-Feature-Ext screen.

When the call is answered, any FNE-based operation can be applied to the call, such as, recall, conference or transfer. After the conference or transfer, the cell phone call remains an OPTIM call associated with the calling station.

The user receives intercept tone for invalid calls to the Mobile Call Feature Extension, such as a call initiated from off the switch, or from a desk set that does not have a supported OPTIM application administered.