You just press it and the chime unit goes "Ding Dong".
Not only that, but an LED lights up.
Whatever will they think of next?
(Admittedly, the enclosed instructions were rubbish and incomplete).
I needed this as a replacement for an identical bell push that had broken due to water ingress.
There is a technique for matching up the bell push with the chime unit.
The instructions totally ignore such a scenario, although I would imagine that the only reasons for buying a wifeless bell push, is to either replace a broken one, or to add another for another door.
If I remember correctly, there were two buttons on the chime unit. I pressed both of those at the same time as pressing the bell push for about 10 seconds, and after that, the units were synched together.