Voice Short Codes
(VSC) - Like they do with SMS and MMS, interactive TV programming can use VSCs for enhanced user participation. For participation TV use, VSCs are typically activated by the end-user using their mobile phone or another enabled mobile device. (Many mobile devices are incompatible with VSC.)

With a VSC, users only have to call a 5-digit number which can be easier to remember than standard phone numbers or premium rate numbers. This means that users could be more likely to remember the VSC and re-use the service.

Customers pay for Voice Short Code calls as they do with normal calls; either on their mobile phone bill or from prepaid credit. Call revenue is typically shared between the mobile network operators and the content provider(s).

A single five-digit Short Code can be branded as a complete means of mobile interaction through SMS, MMS, voice and video. 

Voice Short Codes allow you to combine voice and data components for a campaign or application and thus can complement existing SMS (Short Message Service) and MMS (multimedia messaging system) Short Codes.

At the time of this writing, VSC was most readily found in the UK.