The Honeywell 1321-1 is a 16.5VAC @ 25VA power transformer designed for use with VISTA-Series control panels. The 1321-1 replaces the discontinued 1321 model number.
Q & A's : 1321-1 - Honeywell Home Plug-In 16.5VAC @ 25VA Power Transformer (for VISTA-Series Control Panels)