atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Security, Alarms and Paging End of the line resistor

I would like to understand the purpose/advantage of having 'end of the line' resistor(s). Thank you.

It allows the system to monitor the line. An open or short will change the line resistance and set off a trouble alarm.

^^^^ And it will generate an alarm if the system is armed.

And as the name suggests it goes at the END of the loop, NOT in the panel.

Ummm...it can go in the panel (in fact that's where I always put them) if you use quad wire for the loop. The loop goes out on R/G, makes a U-turn and returns on the B/Y, so that's the end of the loop. The resistor goes on the B/Y in the box.

No professional would install them in the panel! Yes it can be done but negates true line/loop supervision.

Read it again, please. It does indeed supervise the loop. It is electrically equivalent.

I understand that the resistor can be put right across the terminals of the loop, cheating, so to speak, but that is not what I am describing.

The loop travels out from the screw terminals in the panel, on the R/G, to the last device, then changes color to the Y/B and comes directly back to the panel, uninterrupted.

It makes trouble-shooting easy because the entire loop, including the EOL resistor (or diode) is visible and accessible.

1. It does not require trying to find which device is the actual EOL device in an unfamiliar installation.

2. If the resistor or diode fails, it can be easily replaced, right at the panel.

3. If a device needs to be added, the new quad wire is installed from the (former) last device to the (new) last device, and the installer loops back the Y/B at the new device. The resistor or diode remains untouched in the panel.

4. You can trouble-shoot the integrity of the entire loop right from the panel, since you are actually looking at the end of the loop.

There are lots of professional companies doing it this way.

actually If you do it how Arthur states you still Maintain supervision. This is how I do my window and door contacts in non UL installs. wire the panel red/black and the contact red/green. the circuit starts out on red travels to the contact, wire one side of the contact red the other green. short the black/yellow pair at the contact. back at the panel install the eolr between the yellow/green pair. If any of the conductors are shorted and damaged it will fail to see the resistor.

This has always worked very well for me, any damage to any conductor will show a fault..again this is for non UL installs

Glad to see some interest in the correct use of an EOLR. I first started working in the alarm industry in the late 70's and was trained well in ground loop wiring. I would be proud to work behind Anthony or Arthur's work.... Unfortunately, I know of NO company in my areas that use the EOLR correctly.