Power Simplex 4050 on Simplex 4010

I would like to be able to power my Simplex 4050’s off of my 4010 panel but am not clear on how to do it. My ideal scenario would be to have a relay with AC power fed into it and have a NAC wired to the relay so when 24vdc is passed into it, it closes the contact on the relay and then allow the AC power to then be run to the horns. This would be best so I can code the horns because continuous is way too much on these horns. 105 db+ per horn! My question is which relay would be best for this and what model number is it so I can buy off of ebay or a place like that?


Trying to operate old AC notification appliances from a panel not meant to do that can be tricky. Adding a relay to a NAC is quite easy. A 24 volt DC relay coil and 2 diodes. One diode to block the reverse polarity supervision voltage and a back EMF suppression diode across the relay coil.

Before a relay and other parts can be recommended the specs on the horns are needed. There should be a data plate showing the voltage and current rating of the 4050 horns. Also need to know how many of those horns you are wanting to operate. Those items are needed to select a relay with the correct current switching capacity and a transformer to power the horns.

Another problem you’ll face is the AC NAC circuit cannot be supervised without another relay, a variac of some sort, and a monitor module. I won’t go into specifics but to properly supervise this AC circuit would require some fancy electrical work. Obviously for a hobbyist setup supervision is less of an issue (although personally I always recommend it, proper wire supervision gives me a reason to do the wiring properly and helps troubleshoot opens and shorts in the loop).

When you’re connecting these relays make sure that they are rated to handle the voltage and current you need, you would NOT want to risk AC voltage leaking into your 4010’s field wiring.

Here’s an Amazon link for a solid state relay:

<LINK_TEXT text=“https://www.amazon.com/GEREE-24V-380V-S … 4vdc+relay”>https://www.amazon.com/GEREE-24V-380V-SSR-40-Solid-Module/dp/B00RHBEDJE/ref=sr_1_11?ie=UTF8&qid=1508555248&sr=8-11&keywords=24vdc+relay</LINK_TEXT>

This relay would certainly be able to handle your AC signals, can be switched by a DC signal between 3 and 32 volts, and being solid state, will lend itself much better than a traditional SPST relay to coding since it doesn’t have traditional contacts that will wear out with constant switching over time.

If you’d rather use a traditional SPST relay, here’s another:

<LINK_TEXT text=“https://www.amazon.com/Functional-Devic … 4vdc+relay”>https://www.amazon.com/Functional-Devices-RIB2401B-Enclosed-Relay/dp/B000LEUJU6/ref=sr_1_5?ie=UTF8&qid=1508555248&sr=8-5&keywords=24vdc+relay</LINK_TEXT>

As Retired STR-SG said, a blocking diode would be a good idea for the relay input to keep supervision voltage out of the contacts, and an EMF supression diode would be a good idea as well for the conventional relay. I’m not sure if you’d need an EMF supressor for a solid state relay since there’s no magnetic fields involved.

Thanks for your replies! I completely forgot about supervision and how AC signals are incompatible with that. I’ll keep the relays in mind but I’m investigating older panels or older NAC extenders that would natively handle this type of application.

You never mentioned the voltage and current specs on your AC horns. If they are from a system that operated series AC horns I can suggest 2 Simplex items to look for. I know that other old systems used series AC horns but I have no knowledge about their inner workings.

A 4208 H module operates series AC horns and has 24 volt DC control relays. I have adapted several of these to be controlled and supervised by a DC NAC on a new panel. The H module is easy to identify. It will have a small circuit board on the left side and one or two Variac adjustable transformers.

The 2001-2077 AC signal module was made for the a 2001 to be able to replace a 4246 or 4208 panel and keep the AC horn circuit in operation. This would take more adapting than the 4208H to get the control and trouble circuits wired into another panel. The connections are on a 16 pin socket that is very difficult to find a mate for.

Retired STR-SG,

Sorry about that, they’re 12 volt AC and 1.5 amps each 60hz. I saw a couple of old fire panels on e-bay as well as an old Signal extender. The signal extender model is labled SU.

Yep, those are from a system using a series AC horn circuit.