I think you mean loops. ERS loops(the circuits on which the boxes are on. Called loops to differentiate from Circuits that the pull boxes are on) have to have a certain voltage and amperage to operate. They are usually 100 volts, 150 milliamps. 601 is the foreman. I presume he was out working with his crews to trouble shoot a few loops in a particular feeder cable. If you hear a loop or circuit is open, that means there is a break somewhere and the loop is not getting the electricity it needs. If you hear shunted, it means the loop or circuit is getting electricity, just an insufficient amount.
If you hear us place battery on a loop, or a ground, we have grounded one side of the loop to try to close an open loop(circuit). We can either ground out the negative side(also called positive battery) or the positive side(negative battery). Grounding out the loop(circuit) allows alarm boxes to still come in on one side of the break so we don't completely lose alarmbox coverage. It also allows the electrician to better find the break in the circuit to repair it. There's a lot more to being an FDNY Fire Alarm Dispatcher than just telling the guys in the rigs where to go.