Calls per second (CPS)

Calls per second, usually written as CPS, is a limit your carrier sets on how many brand-new calls you are allowed to launch each second. It is a rate, not a total. A carrier might let you run hundreds of Concurrent calls at once but still cap you at, say, 10 new calls per second. The two limits are separate, and you can hit either one.

Carriers use CPS to protect their network from sudden floods. When a Predictive dialing campaign ramps up, your dialer can try to fire a large burst of calls in a single moment. If that burst exceeds your CPS limit, the carrier rejects the extra calls, often returning a CONGESTION response. Those rejected calls look like failures on your side even though nothing is wrong with the leads.

Staying under the limit

If you see calls failing in bursts but succeeding the rest of the time, a CPS cap is a likely culprit. The fix is usually to ask your Carrier to raise the limit, or to spread your dialing across more than one SIP trunk so no single trunk takes the whole load. Some setups split traffic across two carriers to double the effective CPS ceiling.

Keep CPS in mind alongside your Channel count when you size a campaign. Channels limit how many calls live at once; CPS limits how fast you reach that number. A floor that needs to dial aggressively at the start of each hour will feel a tight CPS limit before it feels a channel limit. Knowing both numbers up front saves you from chasing phantom call failures later.