Is the Edwards/EST 792 electromechanical or electronic?

As with the other electric horns, their individual sounds can vary. Every snowflake is different, not all alarms make the same sound.

1 Like

Except most other electric horns all have the same pitch. Were some SHGs just designed differently from the others? I have never heard two TrueAlerts sound different nor have I heard two Spectras or Genesises.

1 Like

Double post but I don’t care.

Apparently electronic horns manufactured in the early 1990s may have different pitch variations but late 1990s horn all have one pitch. Somebody correct me if this is wrong.

I think the volume of the device and the surroundings affect the sound. Destin’s SHG was right up next to the microphone, but Charlie’s was not.

But why would it only affect some horns and not others? If you were to do the same thing with a standard TrueAlert, there would be no variation. Is it something to do with the fact that it was manufactured in the late 1990s and not the early 1990s?

Here’s another example: Destin’s video of a multi-tone TrueAlert sounds different with the two volume settings.

1 Like

But I was talking about normal tone alarms. The normal tone TrueAlert has no other pitch change. I think it has to do with what the year the horn was made. Compare the 4 SAE HA2VD videos on YouTube

All of them have different pitches.

Volume has nothing to do with it at all. The SHG has an analog tone generator (at least I’m pretty sure it does), and analog oscillators drift in pitch. Digital tone generators never vary in pitch because it’s microcomputer-controlled.

So Simplex 4051, you’re mostly right. It has to do with if the horn is analog or digital, but any horn that has a potentiometer is also subject to pitch changes because not all of them can be turned to the exact same setting.

I don’t remember those Space Age horns having potentiometers, so they could very well be analog.

Destin, I’m curious- how does an analog tone generator work? Does it simply oscillate the frequency with solid state equipment?

So I take that to mean that if an electronic horn has an analog tone generator, the pitches will change from horn to horn then?

Also, were the analog tone generators only used in the early 1990s before being replaced by digital tone generators?

  • Just to clarify, this is speculation on my part. I’ve never torn apart any horns to see what kind of tone generator they use or how the pitch is regulated. I’m just making inferences based on what I know about audio and synthesis.

Yes, an analog tone generator uses solid-state analog circuitry. Analog oscillators repeat an electronic signal at a certain frequency, creating a waveform. The higher the frequency, the higher the pitch. Considering that the first electronic horns were developed in the 80’s, I suspect that they use digitally-controlled analog oscillators. This means that a microprocessor is used to regulate the frequency, but the method for tuning analog oscillators is fairly relative and still won’t achieve the same pitch accuracy as an all-digital tone generator. Long story short, horns with analog tone generators can vary in pitch from device to device.

A digital tone generator basically does the same thing, but instead uses digital signal processing. In the case of modern horns like the SpectrAlert Advance, more complex methods of synthesis such as frequency modulation are used to create rich harmonic variation. Digital tone generators will never change in pitch, unless the horn has a potentiometer that has been adjusted (a wheel on the circuit board that changes the pitch).

During the early days of electronic horns, analog tone generation was probably less expensive than digital, so it would have been more common in the late 80’s/early 90’s. It was also common in voice evac systems until everything went to digital playback. These days, digital tone generation has replaced analog in fire alarm notification, although I don’t know if that’s true for certain chime/strobes. Again, all speculation.

So Destin, in your opinion based on the 4 videos I posted, would the SAE HA24Ds have analog instead of digital? Though finding out when were they first manufactured as that would be a good starting point.

1 Like

I think so. I have an HA24D from 1994 that sounds different from all of those videos, so I would imagine that at least a certain part of the tone generation is analog.

Au Contrare. The Edwards 894b-226 is looks like an 892 but it is electromechanical like the 870’s(Adaptahorns).



1 Like

Aren’t the electromechanical 800 series like super rare? There is only one video on YouTube that has them.

I’m thinking that pre integrity of 792 is actually electronic, which it is not electromechanical though.

I’m 10 years late but I’m pretty sure most, if not all newer electronic horns use a programmed microcontroller to generate sound. The SHG just uses a simple 555 or 556 timer circuit.