Example Double Insulated Bell Chime Transformer Part Number DAT01A (Greenbrook.co.uk)
In-built thermal cut-out, short circuit and overload protection self re-setting. 4/8/12V AC Output @ 1A.

Datasheet https://www.greenbrook.co.uk/mpattachment/file/download/id/46/

Available from a number of distributors, example https://www.tlc-direct.co.uk/Products/TCTR7.html

Mains Input
246.2V RMS AC 

Secondary Output
4 = 6.4V RMS AC    	
8 = 12.8V RMS AC	16.43 DC
12 = 19.23V RMS AC	

The 12V Output setting performs the best and IPEM ATM90E32 and ATM90E36 VP Input has been designed for this.

Note: IPEM AP SMPS Regulator Input Voltage, Absolute Max: 32 V DC

