Glossary · Telephony & India rules
How do caller ID and number pools work?
Caller ID (CLI) and number pools
Caller ID, or CLI (calling line identification), is the number a person sees when your call rings. A number pool spreads your outbound calls across several numbers, so no single one calls too many people too fast.
On a call
A shopper misses your agent's call about her abandoned cart and rings the number back that evening. If the call came from your own number, your inbound agent picks up. If it came from a shared line, she reaches someone else's business.
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Explained
Here is how it works, in plain words.
The number on the screen decides whether people pick up. A local mobile number gets answered. A number that’s been reported as spam, or that rang a hundred people this morning, often doesn’t.
Networks and caller-ID apps watch how numbers behave. A person on a sales desk makes a few dozen calls an hour to different people. A single number placing hundreds of calls an hour looks nothing like that, and it starts collecting spam tags. Once tagged, its answer rate drops for everyone it calls.
TRAI now does this formally. Under its 2026 amendment, operators run AI systems that flag numbers likely to be sending spam. When several of one sender’s numbers get flagged in a short window, the operators start checks on that sender, which can end with outgoing calls barred on all its lines. Numbers from the series set aside for commercial calls, such as the 140 series, are never flagged as spam to the people receiving them.
A pool is the software answer to the sales-desk pattern. You group several numbers, set how many calls each may make in an hour and a day, and the dialer spreads the campaign across them. Two details matter. Retries to the same person should come from the same number, so a missed call they return still reaches you. And a number whose answer rate falls far below its siblings should rest before it’s burnt.
The source number also decides where callbacks go. People return missed calls all the time, especially in India. If your agent called from your own number, an inbound agent on that number can answer. A shared line can’t do that for you.
Be honest about the source, too. TRAI treats commercial calls from ordinary ten-digit numbers by an unregistered sender as spam. Register, and use the right series for promotions.
In Voice Infra
This is what Voice Infra does about it.
Pools spread outbound calls over your numbers at the hourly pace you set, and a contact's retries come from the number that rang them first. A number people stop answering gets rested before it's burnt, and a new one warms up at half pace for its first week. Calls from the Mirai shared line show a number other businesses use too, so callbacks to it won't reach you.