Calculate the velocity of your outbound campaign.

CPS is the number of new calls your telephony provider lets you start every second. It is a setting on the provider side: with Twilio, for example, the default CPS is 1, and you can usually ask your provider to raise it. CPS multiplied by your phone lines or SIP trunks and by 60 gives the maximum number of calls you can launch per minute.

A concurrency line is one agent slot: the number of concurrency lines is how many agents you can deploy to be calling at the same time. It is different from a phone line or SIP trunk, the number or connection the calls go out through. With CallShift, 10 concurrency lines are included by default with every workspace.

A phone line is an outbound phone number used to place the calls; a SIP trunk is the connection that carries them between your telephony provider and your voice platform. Both are different from a concurrency line, which is an agent slot. Depending on the provider, the CPS limit applies per trunk, per number or per account: where it applies per trunk or per number, spreading a campaign over several of them raises the pace.

Because a dial takes its concurrency line from the first ring, not from the moment someone picks up. While the phone rings, the AI agent is already up and waiting and the call holds a slot on your SIP trunk, yet nobody is talking. Each dial therefore keeps a line busy for the average ringing time plus the average call duration: with 13 seconds of ringing and 14 second average calls, a dial holds its line 27 seconds, and for nearly half of that time nobody talks. It is not talk time, though, so it does not add to the voice minutes the campaign consumes.

The lower of two ceilings: the provider CPS limit, which caps how many calls start every second, and your concurrency lines, which cap how many calls can hold a line at once. Ringing counts toward the second, since a dial holds its line from the first ring. With a CPS of 1, 13 seconds of ringing and 14 second average calls, 27 calls hold a line at once, so 10 concurrency lines are the bottleneck: adding lines speeds the campaign up until the CPS takes over, and from there only raising the CPS with your telephony provider does.

Multiply your CPS by your number of phone lines or SIP trunks and by the seconds each dial holds a line, that is your average ringing time plus your average call duration, then add the lines you reserve for inbound calls. Example: with a CPS of 1, one phone line or trunk, 13 seconds of ringing, 14 second average calls and 3 inbound lines, you need 30 concurrency lines: 27 for outbound calls, ringing or talking, plus 3 for inbound.

Compare two paces and keep the lower one: outbound concurrency lines times 60 divided by the seconds each dial holds a line (average ringing time plus average call duration), and CPS times phone lines or SIP trunks times 60. That minimum is your real pace in calls per minute. Divide the total calls in the campaign by it to get the campaign duration.

A callback is an inbound call from a prospect who missed your call and dials your number back. Callbacks are frequent during an outbound campaign, so it is best practice to keep a share of your concurrency lines free for inbound. The simulator reserves (1 - average pickup rate) x 10% of your lines, rounded up: 8% at the default 20% pickup rate, more when fewer people pick up, and nothing at 100% pickup since nobody calls back.

Cold calling consumers in France is allowed Monday to Friday, from 10:00 to 13:00 and from 14:00 to 20:00, and never on Saturdays, Sundays or public holidays (French decree 2022-34, in force since 1 March 2023). That leaves 9 hours of legal calling per weekday, so a campaign longer than that has to be split across several days. The simulator warns you when the start time you pick, or the finish time it computes from your pace, falls outside those windows.

It can be multifactorial, but very likely your orchestration platform applies its own operational margin (or latency) to process all the calls: terminating a call, checking the next contact, warming up the new agent, launching the call. A reasonable approach is to apply a 10 to 20% margin to the theoretical velocity from the simulator.