Help with 1960s Ellenco FA System

Hi all, I’m an industrial electrician and working with a Fire Alarm installer trying to figure out a “Trouble” situation on an old Ellenco system in a Maryland school. The system has been in this state for ever and we are being asked to remedy it. System is 1960s vintage.

We have disconnected the pull station circuits and jumpered the terminals for each with a 4500 ohm resistor. We still have trouble.

The panel has a bunch of wire wound resistors which are used to adjust the current to the gong/bell circuits. The panel does not have a code wheel, just a bunch of 120V relays. 5 pull zones circuits, 6 gong circuits.

My question is: are those gong/bell circuits supposed to be supervised using resistors or diodes across the bells?


Couldn’t figure out how to edit so here is some more info.

All the relays have been cleaned and are working correctly.

We have tightened a bunch of connections and reflowed some dodgy solder joints.

There are a set of connections on the right hand side labeled C, S, Z1 through Z5 and G. These are for an annunciator which is not connected. Should any of those be jumpered? We’re reluctant to experiment and start blowing fuses and welding contacts closed.


Typically systems of that age use series AC signal circuits. The adjustable resistors to set the current point in that direction. In these circuits the bells, horns, or whatever are a low voltage AC at some current rating. Look at a signal device data plate. If it says something 6 Volts AC 1.8 Amps it probably is a series AC circuit. These circuits do not use an end of line device. Rather, if complete, the circuit activates a gong circuit supervisory relay in the panel.

There may be only one relay for all the signal circuits. That is how an old Simplex 4247 system is set up. In supervisory mode the signal operating relay contacts are arranged so that all the resistors and all the signal devices form one big series circuit. If all is well the supervisory relay will activate. I don’t know if the Ellenco is set up that way or uses a separate supervisory relay for each circuit.

I doubt the annunciator outputs are supervised. On old Simplex AC systems they were not, and I don’t know of any others that were supervised. If they are, jumpers would have been installed in the 1960s when the system was installed.

I only worked on one Ellenco system in my entire career. It was a circa 1970 system with about 25 zones. And it was in trouble. I found that the contacts in one of the zone supervisory relays was not closing. I had to take the relay apart to adjust the contacts so they would close when the relay coil activated.

Are the box circuits on the left hand side of the panel and is the back plane slate?

Some of those old high voltage panels are all in series. If the old pull stations are coded, they may be wired normally closed and open the circuit momentarily to ring the bells. If this is the case, try putting a jumper across the pull zones instead of the resistor.