Multi-line

A multi-line system handles several simultaneous communications: several numbers or channels on the same equipment, several calls in parallel. Historically it was a physical switchboard with buttons; in VoIP, the very notion of a "line" dissolved — the SIP trunk provides as many simultaneous channels as the plan allows.

The confusion to avoid: more lines doesn't mean more answered calls — a six-line system with one person answering still produces five missed calls. Multi-line answers technical occupancy; the answer to human occupancy is routing — sending each call to someone or something able to handle it: a second extension, a voice agent, an instant text-back.