Some of my alarms have four pigtail leads – one for wiring up to a non-speaker audible appliance, and the other for power. Examples of alarms that follow this criteria would be my Simplex 4904-9101, my 4903-9101 strobe plate, my 4903-9102 light plate, etc. Whenever I use such alarms as either the last device on the circuit, or the only device on the circuit, I am left with just one pair of pigtail leads which never gets used.
In the past, whenever I run into situations like this, I usually cover up said unused pigtail leads with small bags or boxes.
My question is: what should I do to the unused pigtail leads to ensure my safety?
Normally the unused pair of leads would connect to the end-of-line resistor (EOLR) on the panel circuit. Since you just use a power supply, twist a wire-nut onto the end of each lead (don’t connect them together). If you don’t have enough of these available a piece of electrical tape would work just fine.
Alternatively, you could just twist both pairs of leads into the connection to the circuit wires. They are soldered together on the board anyways, so connecting both red wires to the positive feed and both black leads to the negative feed wouldn’t make a difference, you wouldn’t have to worry about the unused leads anymore.
Obviously, as I mentioned earlier, on a real system you should not use these methods, instead connecting an EOLR to the leads.