atcomsystems.ca/forum Forums Other TDM Phone Systems Executone-Isoetec Telephones & Systems Audio Transformer Specs

Folks, I'm trying to find the specs for an audio transformer. The transformer is used with an Executone Phone system that's being utilized as an elevator intercom for a large 4 building complex, installed circa 1990. The transformer is used in two places, between the speaker and a Valcom 2900 intercom located in the elevator cab, and in conjunction with a Valcom 1109 Zone paging unit for all-zone paging to the cabs.

The transformer pt # is A-2225, a web serch produced no results. Is anyone familiar with this transformer and how it's used in the Executone/Valcom application?

Regards, Jim

James;
I can't say that I have heard of an A-2225 transformer from Etone or ever seen a need for an "audio transformer" in an Executone elevator application. I will say that the Valcom stuff is pretty straight forward & will only need -24VDC power supplies & some connection to an audio path to the phone system (typically connected to a C.O. port in the phone system).

You said that the transformer is used in 2 places so my first guess would be for the power supplies for the Valcom but if thats not the case it might be hooked up to an auto dialer used to dial an external number (I.E. 911, security) in the event that the elevator button is pushed.

All of this id strictly speculation so if you have a picture I might be able to figure it out.

I second the picture , sounds like some type of special circuit, I can remember hooking up elevator phones with Ring-down circuits. But we never used any Valcom parts.

Question Have you contacted Valcom Tech support?

Based on your description of the site "large 4 building complex", I suspect that the cable run from the zone paging unit to the elevator is probably very long. The original installer may not have been able to get adequate signal strength between the 1109 and the 2900. I suspect the transformers were added (with or without the sanction of Valcom) to circumvent the signal losses in the cable.

You don't say why you are trying to find the specs on the transformer, but if my assumptions are correct, one side of the transformer would need to match the impedance of the Valcom devices (600 ohms? 45 ohms?). The other side would need to be a lower impedance. The lower impedance side of each transformer will connect to the cable pair between the buildings. The higher impedance side will connect to the Valcom devices.

The value of the lower impedance side of the transformer is not specifically critical. However, if you need to replace a transformer, you will need to replace both transformers with a matching pair.

Gentlemen thanks for the reponses. I agree the transformer is used for impedence matching. In the elevator cab it's connected beween an 8 ohm speaker and the Valcom device, so an 8 to 45 ohm impedence match. The confusing part is why it's used beteen the Valcom 2900's in the cabs and the Valcom Zone pager.

There is a DPDT relay on each tip and ring (66 elevator cabs and 66 relays). When the relay is energized the T & R are switched to the zone pager where there are 5 of these transformers. I believe the tranformer completes the loop which causes the Valcom 2900 to go off hook and allow for a page. My problem is that the wiring between the pager/transformers and relays has been cut and I now need to replicate this setup. I don't know if the zone pager fed all 66 elevators via the 5 transformers or only a subset - 1 to 4 or 1 to 8 elevators etc.

Has anyone seen this setup somewhere else?

Regards, Jim

You ARE working with a very unconventional configuration. :confused:

Is it possible they used the relay to switch between all call/zone paging from the 1109, and normal intercom operation of the 2900 (Using, of course, the 2900 speaker to receive the page signal from the 1109)?

What is used to energize the relay?

Would certain elevators have a need to receive paging and others not need to receive paging?