Understanding SIP Trunking vs Traditional Phone Lines

Traditional POTS (Plain Old Telephone Service) lines provide one call per physical line and are increasingly expensive and discontinued by carriers. PRI (Primary Rate Interface) carries 23 simultaneous calls per circuit over a T1 line — common in larger businesses but also being phased out. SIP trunks carry voice calls over your existing internet connection with no physical voice infrastructure required. Advantages of SIP trunks: add or remove concurrent call capacity (channels) quickly without physical work, typically 50-70% cheaper than equivalent PRI capacity, geographic flexibility (use any area code regardless of physical location), and built-in disaster recovery (calls can be re-routed to mobile numbers or another location if the office is unreachable). SIP trunk selection criteria: call quality (ask for a trial), support responsiveness, pricing per channel vs per minute, geographic coverage for outbound caller ID, porting support, and contract terms. Tier 1 SIP providers (Twilio, Bandwidth, Vonage) offer better call quality and support than budget providers. Match the number of SIP channels to peak concurrent call volume — running out of channels during peak hours results in busy signals.