The INDeX IP Softphone provides a high level of the functionality of a 20xx series handset on a user's PC desktop. The Softphone connects to the INDeX using the IPNC cassette with voice compression modules. The INDeX can support 120 IP Softphones (20 per IPNC, 6 IPNC's per INDeX System).
Most of the features associated with the 20xx series handsets are available (e.g. Park, dial ahead, DSS/BLF, Callback etc) and some additional features:
A licence key is required on the INDeX to support the Softphone. The first Softphone can be used without a licence key.
The AVAYA 4602 IP phone offers all the functions of a standard telephone, but using VOIP technology. This enables the implementation of extensions into remote offices, allowing administration from a central point, without the additional cost of remote PBX's.

| Speaker: | Switch to speaker (Not Handsfree) |
| Message: | Used to leave or return messages |
| Hold: | Used to hold calls |
| Mute: | Used to mute outgoing speech |
| Transfer: | Used to transfer a call to another extension |
| Conference: | Used to set up a conference call |
| Drop: | Used to clear a call |
| Redial: | Used to redial the last dialled external number |
The call control and call routing functions associated with a standard telephone are also supported by the 4602 IP Phone.