Hertz Electric said:
...But is what I described above what a t-tap is called.
Yes.
I concur with the other responses.
However, I have never seen a "loop" that returns to the panel, but I'm far from an expert, and have never worked with Edwards equipment. My experiences have been with Simplex/Grinnell and Notifier systems, and very limited at that.
As I understand it, Class A wiring, the kind you cannot T-tap, typically utilizes an
End
Of
Line
Resistor connected across the end of the two leads, at the last device in the circuit, so the panel can place on and monitor a current through the loop. The panel will indicate a fault should that current drop to zero (open circuit) or become too high (short circuit).
I believe Class A wiring is typically used on loops having non-addressable devices. In the case of addressable-device loops, the panel will indicate a fault if the device fails to respond to a status check, which is performed at short and regular intervals ...so a circuit-checking current is not necessary.