Q: Is there a way to connect an external high-temp alarm / warning light?

A: Yes. When the unit goes into alarm mode it also trips an external relay that can be connected to a horn / light on terminal 10 of the unit. The HSM module has a 2A Normally Open (N.O.) output contact that can be configured to close when any of your program temperature thresholds is exceeded. See below for more information.

HSM Terminals 6-10 for Alarm