carriers-sip
Concurrent calls
The number of separate phone calls running at the same moment on your system, which sets the real ceiling on how busy your call center can get.
Concurrent calls is simply the number of phone calls happening at the same time on your system. If you have 30 agents talking and another 20 calls ringing out, you have 50 concurrent calls. This number matters because it is the real limit on how much work your floor can do at once, and it is what your carrier and your server both have to support.
Every concurrent call uses one Channel on your SIP trunk. So if your trunk is rated for 100 channels, 100 is your hard ceiling for concurrent calls on that trunk. Go past it and the next call fails. This is why people often talk about channels and concurrent calls in the same breath — one is the capacity, the other is how much of it you are using right now.
With Predictive dialing, the dialer launches more calls than you have agents, because most calls will not be answered. The Lines per agent setting controls how aggressive that is. Dial too hard and you can blow past your concurrent-call limit, which causes Drop rate problems and failed calls. Tuning this is a balancing act covered in more depth in the drop-rate playbook.
Concurrent calls is different from Calls per second (CPS), which limits how fast you can start new calls rather than how many can be live at once. You can have plenty of free channels and still get throttled if you try to launch them too quickly. When you talk to your Carrier about capacity, ask about both numbers — your concurrent ceiling and your per-second rate. If you want practical pacing advice, see how to lower your VICIdial drop rate.
Related terms
Carrier
A carrier is the phone company that actually carries your calls onto the public phone network — VICIdial dials, the carrier delivers.
Channel
A single call path on your trunk, where each live call uses exactly one channel, so the channel count is the cap on how many calls can run at once.
Calls per second (CPS)
A limit on how many new calls your carrier lets you start each second, used to protect their network and keep your dialing from getting throttled.
Lines per agent
A rough way of describing how many simultaneous calls a campaign places for each logged-in agent, closely tied to the dial level.
Predictive dialing
A dialing mode where VICIdial places more calls than there are free agents, predicting how many will connect, to keep agents busy.
SIP trunk
A virtual phone line over the internet that connects your dialer to a carrier, letting you place and receive many calls at once without physical wires.