Audio annunciator suppression.

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In summary, the electrican wants to locally suppress the annunciator tone, but still receive the message. He tried using a standard bridge rectifier to power a 5V relay, but the relay would not pick up. He then went to a Picaxe chip and programmed it to detect the low input on one of its pins when the input tone matches 950 Hz. He then attached the input line to the 567 tone decoder chip and ran it to the speaker. If the input tone doesn't match 950 Hz, the Picaxe will disconnect the relay. Therefore, if someone talks on the PA, the electrican plans to leave the relay pulled in for the amount of time it would take for the person to talk.
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XYZ343631
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I am searching for an easy solution for an exasperating nuisance.

There is a public address system at work and before the start of the messaage a loud audio annunciator frequency has been added to warn people of the upcoming message and I want to locally supress it but still receive the message.

The speaker is located just above my shop and do not want to interfere with the global annunciator but only this one speaker.

I am an electrican who was trained in electronics decades ago and my idea is that when the annunciator tone is present, rectify it and pick up a relay that starts a delay on timer that blocks the signal until timing is completed.

The annunciator tone is app. 900HZ to 1000HZ and centered around 950HZ as measured with an o'scope. The annunciator tone lasts for one second and is very disturbing and want to cancel it during that time and then have the timer close the circuit again to hear the message. That is it in a nut shell.

I tried using a standard bridge rectifer powering a 5V relay but the relay would not pick up and if I can pick up the relay then the local problem will be solved.

Please give me advice on how to accomplish my goal which will make all of the electricans happy in the electrical shop. Thanks for any and all responses.
 
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  • #2
Would it be easier to just put a notch filter inline that attenuated 950Hz, wouldn't have to be very narrow so not hard to design.
It would distort the voice a bit but should still be recognizable

The trouble with detecting the tone and turning it off is that unless you do some clever analysis of rise time etc, just detecting the frequency would mean you would also turn off the speaker when the person talking happened to hit that note.

- pf readers are all over the world in different time zones, but mostly in USA/Europe - so depending when you post you might have to wait 8-12 hours for anyone to see it.
 
  • #3
XYZ343631 said:
I am searching for an easy solution for an exasperating nuisance.

There is a public address system at work and before the start of the messaage a loud audio annunciator frequency has been added to warn people of the upcoming message and I want to locally supress it but still receive the message.

The speaker is located just above my shop and do not want to interfere with the global annunciator but only this one speaker.

I am an electrican who was trained in electronics decades ago and my idea is that when the annunciator tone is present, rectify it and pick up a relay that starts a delay on timer that blocks the signal until timing is completed.

The annunciator tone is app. 900HZ to 1000HZ and centered around 950HZ as measured with an o'scope. The annunciator tone lasts for one second and is very disturbing and want to cancel it during that time and then have the timer close the circuit again to hear the message. That is it in a nut shell.

I tried using a standard bridge rectifer powering a 5V relay but the relay would not pick up and if I can pick up the relay then the local problem will be solved.

Please give me advice on how to accomplish my goal which will make all of the electricans happy in the electrical shop. Thanks for any and all responses.

The beeper tone should only be used in case of emergencies. Have you tried talking to the folks that manage the audio paging system? You should be able to make a case for only using the beeper for emergency messages. That's how many paging systems are run.
 
  • #4
You could connect the speaker so that it only gets sound if a relay is pulled in.

Then you would need the following:
a source of regulated 5 volts.
a 567 chip
a Picaxe 8M chip
a transistor to pull the relay in.

Run the speaker input line to the 567 tone decoder chip.
This will make its output go low when the input tone matches the 950 Hz expected.

Take this to the Picaxe chip.
Program this to look for this low input on one of its pins.
Look again each 50 mS to see if it is still there.
When it isn't there any more, pull in the relay via the transistor.

Estimate the longest time anyone would talk on the PA and double it.
Leave the relay pulled in for that amount of time. (Easier than trying to detect speech on the line.)

Disconnect the relay.

If the 567 detects another message starting while the relay is still pulled in, the Picaxe can disconnect the relay while the tone is present. However, you may hear the beginning of the tone if this happened because the Picaxe would have to allow a period of 50 mS to be sure the tone was a sustained tone and not an accidental 950 Hz in someone's voice.
 
  • #5
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1. What is an audio annunciator suppression system?

An audio annunciator suppression system is a type of fire alarm system that is designed to suppress and control the spread of fire by using sound waves. This system emits high-frequency sound waves that interfere with the fire's ability to consume oxygen, essentially suffocating the fire and preventing it from spreading.

2. How does an audio annunciator suppression system work?

The system works by emitting high-frequency sound waves that disrupt the combustion process. These sound waves create a dense layer of air that separates the fuel from oxygen, essentially suffocating the fire. This prevents the fire from spreading and gives occupants more time to evacuate the building safely.

3. What types of buildings would benefit from an audio annunciator suppression system?

Audio annunciator suppression systems are beneficial for a wide range of buildings, including commercial, industrial, and residential buildings. They are especially useful in high-rise buildings where traditional fire suppression methods may not be effective, or in buildings with sensitive equipment that could be damaged by water or traditional fire suppression methods.

4. Are there any disadvantages to using an audio annunciator suppression system?

One potential disadvantage of using an audio annunciator suppression system is that it may not be effective for all types of fires. This system is most effective for small, contained fires and may not be as effective for larger fires or fires in open spaces. Additionally, these systems can be expensive to install and maintain.

5. How often should an audio annunciator suppression system be tested and maintained?

It is important to regularly test and maintain an audio annunciator suppression system to ensure it is functioning properly in case of a fire emergency. The system should be tested at least once a year, and any maintenance or repairs should be done by a qualified professional. It is also important to follow any specific guidelines or regulations set by local fire codes.

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