The Siren Board

Posted: **Mon Mar 29, 2021 8:37 am**

(Although this may seem like a story, its a support question)

So yesterday I went and got a Federal Signal Siratrol unit off an inactive model 2 siren (The siren had been removed years ago but the control panels still remained). I got the unit home and tried to get the radio working (I work in radio communication so I own a Motorola Communications System Analyzer Service Monitor R2001D which should give me all the tools I need RF wise). I have no documentation and there is no label on the radio with any technical information pertinent to this individual unit. So, first things first, I needed to find the frequency the radio was aligned to. I connected a cable from the antenna port on the radio receiver to the service monitor RF output. I was able to open the squelch on the radio receiver and use the Service Monitor to generate a 1Khz tone as I swept the frequency band. Once I heard the tone on the receivers internal speaker, I knew I was on frequency. The next step was to try and activate the relays through the tone decoder boards. I have no clue what the frequency tones are used to activate this unit. I thought their might be a reference oscillator on each board for the frequency to match the tone necessary to activate. So, I pulled out my oscilloscope and started probing around on the tone decoder boards. All I ended up finding was the 60hz AC signal to of course power the thing!

So my question is, how would one find out what tones are needed to activate a Federal Signal Siratrol radio tone decoder board? I have literally no clue how to continue and am stuck at this point. Looking for any input from anyone.

Below I have provided some photos of my Federal Signal Siratrol Radio's internals for reference.

This one is just for fun if you wanted to see the rest

Posted: **Tue Mar 30, 2021 4:15 pm**

Update

I found a chart in the manual I didn't see that gives information on how the tones are set. I might be able to reverse engineer the tone decoder boards and find what tone they were set to. The capacitors could be bad so the tones could be out of their defined range. I will post an update with more information if I can get it to work.

Posted: **Wed Apr 07, 2021 4:25 am**

Typically Federal Signal had a printed data decal on the outside of the door on the blue receiver/decoder housing that listed the receiver frequency and tone frequencies required for each function. I have also frequently seen the tone frequencies hand written on paper labels attached to each decoder board relay. Each function required two tones. If memory serves me correctly, the first tone was common with every function and the second tone was specific to each function. Yours is missing in both locations. Other than trial and error. I have no advice.

Edit: I may be off track here, but it appears if you find the value of capacitor 1 (C1) and capacitor 2 (C2) you should be able to reference the chart you have to get you within the tone frequency range. This might get you a bit closer.

Posted: **Fri Apr 30, 2021 1:56 pm**

Interesting that there is a Com-Spec board added to the receiver; likely a PL decoder, so the signal has to have both correct tones AND correct PL tone.

The 3 relays will provide contact closure for each tone; you may have an A-B and A-C sequence, A-B/C-B, Long B or Long C, or any of several others (don't have my Moto pager info nearby about all the different patterns.)

Good catch on the capacitors may be out of whack due to age. Def. something to keep in mind.

Do you know the RF Freq, or where & when it came from?

Posted: **Sat Jun 19, 2021 5:39 am**

Evan Vander Stoep wrote: ↑
Mon Mar 29, 2021 8:37 am
(Although this may seem like a story, its a support question)

So yesterday I went and got a Federal Signal Siratrol unit off an inactive model 2 siren (The siren had been removed years ago but the control panels still remained). I got the unit home and tried to get the radio working (I work in radio communication so I own a Motorola Communications System Analyzer Service Monitor R2001D which should give me all the tools I need RF wise). I have no documentation and there is no label on the radio with any technical information pertinent to this individual unit. So, first things first, I needed to find the frequency the radio was aligned to. I connected a cable from the antenna port on the radio receiver to the service monitor RF output. I was able to open the squelch on the radio receiver and use the Service Monitor to generate a 1Khz tone as I swept the frequency band. Once I heard the tone on the receivers internal speaker, I knew I was on frequency. The next step was to try and activate the relays through the tone decoder boards. I have no clue what the frequency tones are used to activate this unit. I thought their might be a reference oscillator on each board for the frequency to match the tone necessary to activate. So, I pulled out my oscilloscope and started probing around on the tone decoder boards. All I ended up finding was the 60hz AC signal to of course power the thing!

So my question is, how would one find out what tones are needed to activate a Federal Signal Siratrol radio tone decoder board? I have literally no clue how to continue and am stuck at this point. Looking for any input from anyone.

Below I have provided some photos of my Federal Signal Siratrol Radio's internals for reference.

images

This one is just for fun if you wanted to see the rest
image

My advise to you is the locate the audio line going to the decoders which I think is P101 on the decoder modules. Definitely check that, because the manual I have is for the last revision and it's different than yours. Anyway, once you've found the audio pin, start with the signal triggers since they have relays that will tell you when you've found your key. Isolate each module by disconnecting the audio jumper wires, then directly connect them to a sinewave generator of sorts and cycle through the frequencies until they activate. For the common tone, you'll need to find a way to see if it's activating itself or not. You may be able to do that with a multimeter by measuring a voltage difference on it's output line.

Don't bother measuring values of components, that wastes time and has a low chance of getting you the answers. Simulating activations with a generator will guarantee you an answer.

Posted: **Fri Jun 25, 2021 6:11 am**

Tyler wrote: ↑
Sat Jun 19, 2021 5:39 am
My advise to you is the locate the audio line going to the decoders which I think is P101 on the decoder modules. Definitely check that, because the manual I have is for the last revision and it's different than yours. Anyway, once you've found the audio pin, start with the signal triggers since they have relays that will tell you when you've found your key. Isolate each module by disconnecting the audio jumper wires, then directly connect them to a sinewave generator of sorts and cycle through the frequencies until they activate. For the common tone, you'll need to find a way to see if it's activating itself or not. You may be able to do that with a multimeter by measuring a voltage difference on it's output line.

Don't bother measuring values of components, that wastes time and has a low chance of getting you the answers. Simulating activations with a generator will guarantee you an answer.

I worked on it for a few weeks and stopped because I was wasting time. I will get it working someday but just not now. I have already tried what you are suggesting with no success. I completely reverse engineered the schmatics and you will be interested to know that the sine wave that is transmitted and then received by the siratrol is converted to a square wave before entering the tone decoder boards. This is because each tone decoder does not actually decode a frequency, but a voltage. The capacitors that are used to set the voltage detect range are probably shot and I believe that could be the main problem. I also have an aftermarket TS-32 CTCSS tone decoder board that was installed on the radio reciever board. Not sure if that enables/disables the common tone decoder or something else but there is still much more to figure out before I can get it working. When I do, I will make a video explaining what I did. I'm already documenting the entire process for when that time arrives.

Something is off though and is not functioning like normal. I did a full frequency sweep on one of the relay boards (using a square wave at the recommended voltage in the schmatics) and it did not go off at all (I tooke it out of the radio unit and tested it independently). I also made sure to enable the relay board on the pin that would be connected to the common tone decoder board(s). After all of this work, nothing. Something else is broken, I'm sure of it.

The Siren Board

Federal Signal Siratrol Radio Tone Decoder Boards (Need help finding activation tones)

Federal Signal Siratrol Radio Tone Decoder Boards (Need help finding activation tones)

Re: Federal Signal Siratrol Radio Tone Decoder Boards (Need help finding activation tones)

Re: Federal Signal Siratrol Radio Tone Decoder Boards (Need help finding activation tones)

Re: Federal Signal Siratrol Radio Tone Decoder Boards (Need help finding activation tones)

Re: Federal Signal Siratrol Radio Tone Decoder Boards (Need help finding activation tones)

Re: Federal Signal Siratrol Radio Tone Decoder Boards (Need help finding activation tones)