It is possible to have 2 or more doorbells.

If using battery power we do not suggest having more than 15 metres from bell push to doorbell unit. 

If using transformer power then we suggest 8-12 volt transformer with 1 amp output per doorbell used. For example for:

2 doorbells use an 8-12 volt 2 amp transformer.

3 doorbells use an 8-12 volt 3 amp transformer or 3 x 8-12 volt 1 amp transformers.