Walkie Talkie Switch

[atari7202]

I was just pondering the thought of turning one of my walkie talkies into a remote controleed switch and i ripped an old one apart and happend to find that the speaker voltage gets around .3 anyway i was wondering if you could give some suggestions on how to hook up a relay to this i have a 5V relay laying around and would like to use it.

 

[RadioRon]

If this is an FRS type radio, many models come with tone encoding for speaker muting. This means that when the transmit unit sends, it puts a very low frequency tone on the audio which the receiving unit picks out. There are several tone frequencies and if you match up the transmit one and recieve one by programming the radios correctly, then the reciever speaker unmutes only when it hears that tone.

I mention this because one of the biggest problems you will have with any walkie talkie is that it will receive interference from other people's transmissions and you need some way of making sure that your switch control only listens to your transmission, not the others. This tone function is one way to help insure that.

However, in addition, it might be wise to send a simple tone over the radio and then use a tone decoder on the receiver. It would be easy to interface the encoder to the transmit unit microphone and the decoder to the receive unit speaker. The output of the tone decoder would be your switch driver. The old standard tone encoders and decoders are the LM566 and LM567 but there may be newer and better chips now. Perhaps try Maxim.

 

[atari7202]

thanks radioron can you please elaborate on this encoder and decoder i am somewhat of a electronics newbie not to good with microchips and all can you please tell me how i would hook up a encoder and decoder thank you.

 

[Hero999]

A tone encoder is just an oscillator. Ron mentioned the NE566 but the NE555 will do.

A tone decoder is just a filter or PLL connected to some logic that outputs a high when a certain frequency is detected. Ron mentioned the NE567 which is easy to use and can be bought from most component suppliers.

The datasheets for all the aforementioned ICs can be found on the Internet by using Google.