[retrac]

The standard pulse rate is 10 pulses per second. So 999 takes a bit more than 3 seconds to dial. Three seconds is no doubt a long time subjectively in an emergency -- but it is still much shorter than what it replaced -- calling the full number for the the police/fire/hospital, or asking an operator to connect you.

Also in the olden days, call setup and tear-down could take quite a while. Digits to forward and relays to toggle. It could be easily half a minute before the other party started to ring, especially at peak times.