SIP vs PSTN

SIP and PSTN are two different ways a phone call is carried and delivered. Most buyers never need to think about the difference, but it matters when you are deciding how to set up a destination, especially for a call center or agency running higher volume.

What PSTN is

PSTN stands for Public Switched Telephone Network. It is the traditional telephone system: the network of circuits and switches that has carried phone calls for decades, including standard mobile and landline numbers. When you give out a regular phone number as your destination, that number lives on the PSTN.

What SIP is

SIP stands for Session Initiation Protocol. It is a standard for setting up and carrying voice calls over the internet rather than the traditional phone network, commonly used by VoIP phone systems, call center software, and softphones. A SIP address identifies an endpoint the way a phone number identifies a line on the PSTN, but the call travels as data over an internet connection instead of a dedicated phone circuit.

Why this matters when you set a destination

A single agent answering calls on a cell phone is almost always going to use a standard PSTN number as their destination, and never needs to think about SIP at all. A call center or agency running its own dialer or call platform, however, may want calls delivered straight into that system as SIP, skipping a phone number entirely, so calls land directly inside the software the team already uses for logging and handling them.

Call quality is not usually the deciding factor

Both paths reliably deliver a phone call today. The decision is less about which sounds better and more about which fits how your team already operates. If your team already lives inside a call platform with a SIP endpoint, routing calls there directly can be simpler than adding a phone number as a middle step.

How Callmart supports both

Callmart delivers calls to a phone number (DID) or a SIP address the buyer designates, or lets the buyer answer directly in the Callmart browser softphone, which is built on the Twilio Voice SDK using WebRTC. Which options are available depends on the services enabled for the account.

Cost and reliability are not usually the deciding factor

Both PSTN and SIP-based delivery are mature, widely used ways to carry a phone call, and neither one is inherently more or less reliable for a well-configured business setup today. Cost differences mostly show up in the underlying phone or VoIP service the buyer already pays for, not in anything the marketplace itself charges differently based on which type of destination is used.

A simple way to decide which one you need

If you already know what kind of system your team answers calls on, you likely already know the answer. A team on cell phones or a standard desk phone service is using PSTN destinations without needing to think about it. A team running a dedicated call center platform, a cloud phone system, or dialer software that exposes its own SIP endpoint has the option to route calls directly into that system instead. If you are not sure which category your team falls into, a standard phone number as your destination is the simpler starting point.

Neither option requires special hardware purchases specifically for Callmart. Both work with infrastructure most teams already have in place for other business calls.

• You already run a call center platform or dialer with its own SIP endpoint.
• Your team logs and tags calls inside that platform rather than a phone's call log.
• You want inbound Callmart calls to land in the same system as your outbound work.

Carrier

The company that provides your phone service, whether a traditional carrier or a VoIP provider.

Endpoint

The specific address, a phone number or a SIP address, that a call is delivered to.

Common questions