It is the week your mailer lands in Columbiaville mailboxes, or the first real heat wave, or the week after a good story about you runs. The phones light up all at once, your office person is on hold with a supplier, and callers are listening to rings that nobody answers.
With an inbound call center behind your line, the spike turns into a good problem. Trained agents work the same script your best person would use, answer questions, book jobs and tag each call by where the caller heard about you.
When the rush ends you can see what it brought in: who called, what they wanted and which ad or mailer sent them. Your team took care of the customers in front of them, and nobody who called sat listening to an endless ring.