charge for a telephone call
 no-charge call (e.g. via Skype, etc.);  toll-free call
 (telephone) speech quality;  sound quality;  call quality
 intra-city telephone call;  local call
 call-waiting (phone option)
 intercom;  intercommunication system
 phonetic alphabet (e.g. A for alpha, B for bravo, etc.);  phonetic code
 person-to-person call;  personal call
 conference call (phone option);  conference calling
 station-to-station (comms)
 silent time;  silence period
 intercom;  intercommunication system