With most products you can add additional push buttons or additional doorbell units to expand your system or replace parts. 


Please check the below compatibility chart. You can find the model number of your system on the reverse of the product you currently have:


Example:


Product code begins with:Compatible with:
RX, SX or SXi
(RX85, SX80, SX201i.....)
These ranges are discontinued and parts are no longer available. 
DBxxx range
(DB301, DB302, DB333….)
Bell push not available separately.

Compatible with other DBxxx and Bxxx range door chime kits if purchased after 2014.
Bxxx range
(B304, B305, B322....)
Bell push not available separately

Compatible with other DBxxx and Bxxx range door chime kits if purchased after 2014. 
BYxxx range
(BY101, BY202, BY301, BY401….)
Compatible with all BYxxx model door chimes.

Look out for this logo on the packaging:






Additional push buttons are:
BY30, BY32, BY33, BY34, BY35 & BY37
DBY-xxxx range
(DBY-23512, DBY-22321, DBY-22311....)
Compatible with all DBY-xxxx model items that operate on 433mhz.

Look out for this logo on the packaging:





Additional push buttons are:
DBY-23510 & DBY-23610