Depends.
I've had to sit and wait on commercial jobs where they've had to do a 2 hour signal test for the system before installing a pre-payment meter in a pub basement, etc.
In fact, I don't know of any that talk through the wires in the UK, they all use data over GSM. But, that could be a supplier I've not worked with, or a recent change (I've scaled it back as the money is terrible, and the "customers" frequently worse.)
Biting the hand that feeds IT
