CFVCM Network master Handset - Desk MountCFVCM Network master Handset Desk Mount The VoCALL network master handset can be either desk (CFVCM) or wall (CFVCWM) mounted. Each system can have up to 8 master handsets which gives great flexibility to the larger installations allowing all calls to be monitored from various control points. As an example, an installation may have security offices requiring a master handset, reception and numerous entrances that need to be monitored.