For full protection, the input line should contain an external fuse. If one of the DC input lines is grounded, the fuse should be in the opposite, non-grounded line. The example shown is for a system where +Vin is grounded, typically used with a -48VDC input. Note that if the fuse blows, the alarm signal will not operate. Fuse ratings for the 24V and 48V, 15W and 30W models are shown.

