Hi, all. I am by no means an electronics expert so please be gentle!

I need a switch that sits in a circuit with two inputs (input 1= N/A, input 2 = 2 way radio) and a single speaker output.

I want the radio input only to be triggered when a signal is received on the radio or when a user hits a button. So in effect input 1 is always on unless input 2 is triggered by a radio signal or physical depression of a button. Once the button is released or the radio signal stops, i want the switch to flick back to input 1.

Any ideas on such a switch?

I have had this suggested to me, but looking for an expert http://www.fairchildsemi.com/ds/FS/FSA5157.pdf

thanks

 

The manual button operation is easy compared to the "automatic" switching based on a radio signal.

Are you thinking this will allow you to listen to whatever you like until someone comes on the radio, at which time your tunes or whatever are replaced by the radio signal? What sort of 2-way radio is it?

 

hi, yes thats right signal 1 is audio which needs to be always on unless triggered off by an incoming radio signal.
radios are just standard 2 way radios, nothing special.

Got any suggestions on the switch?
Thanks

 

What you need, I believe, is a form of squelch. If this function is not built into your radios already, then you need to make your own. I'm not the person to help with that.

I think if you can get a squelch function working, that on/off signal can be used to switch the audio source as you need.

That switch you linked appears to be meant for switching the power output of the audio system. I would prefer to switch at the level of the input signal, so there is one amp and one speaker, but two signal sources. Would that make sense on your arrangement?

 

Hi wayneh,

thats right, switch at the input level so there is a clear break between the audio output of the ipod and the incoming signal from the radio i.e. 2 signal sources.

Someone suggested using a relay as a switch to flip between inputs, the relay being triggered with a noise on the radio input. the guys in Maplin weren't so sure.

any thoughts?

 

Sound more like a VOX than squelch. If radio is receiving audio.

A search for voice operated relay should be productive.

I'll take a look.



http://www.rainbowkits.com/kits/vox-1p.html

http://www.amazon.com/Ramsey-VS1-Voice-Activated-Switch/dp/B0002NRIN2

 

The Fairchild part has a max signal range of 5V p-p and a peak signal current of 500 mA. This was designed for a cell phone, and will not handle cleanly the signal of a normal 4 or 8 ohm speaker. I agree with inwo, there are a ton of VOX products and projects on the innergoogle to buy or build.

ak

 

thanks for your replies. i checked out the VOX switch; it looks to be right, kinda annoyed i didnt see this when i was already looking at a VOX to avoid having a PTT for transmit mode.

anyway, i found this site (http://circuitsbook.com/voiceoperatedswitch.html) but im not clear on this...

where am i supposed to plug the different circuits to? i.e. vos would trigger connection of the radio circuit, and break the ipod circuit.

perhaps im being dumb

 

The relay contacts aren't shown in the schematic.

Radio output to input of vox.
Connect the speaker to common.
Radio output to NO.
Standby audio to NC.

Or whatever audio levels used switching and sensing.

 

blast from the past...just came across this thread in an old email...

in case anyone's interested, this thread was just the start of my journey into the creation of a product i call the Airwave. you can find out more about here at www.theairwave.co.uk

thanks

 

Wow, that's come a long way in a year. Congrats!

 

a simple way is that if the radio has a light that indicates the radio is reciving a signal, use that as an output to drive a relay. or look at the specs for the radio, most of my ham radios and he buisness band radios I am familiar with have a switched output comming out to an accessory jack already.

 

It would be much nicer to look at the AGC (the signal LED) than voice, then you'd get the switch with the received carrier and music would clear when noise would clear on the radio .. And you'd have the same silence buffer that you'd get on the radio.

 

agc voltage is not normally used for squelch, they use background noise or hiss, which is reduced when recieving a carrier. a high pass filter in the audio line picks off the noise which is rectified and filtered to give a changing voltage when a carrier is recieved,