FM Transmitter that only transmits when a signal is present

[CompuDoc]

What I am looking for is an FM transmitter that only transmits when audio is present. What I would like to do is have the radio in my truck on and have the scanner hooked up so that the audio from the scanner over powers the FM radio signal only when the scanner locks onto an active channel.

Is their such a device?. I do have an FM transmitter that plugs in the cigarette lighter with the audio end going to the earphone jack on my BC246T and the other end going into the power jack on the scanner which is good because it is not running off of battery power. The problem is that the transmitting circuit is always on so all I would hear is the scanner when it locks onto an active channel and not the radio station it is tuned to when the scanner is not locked onto an active channel.

I guess what I am looking for is something similar to when someone takes a cell phone call that comes over their radio the music is interrupted and the audio from the call can be heard.

 

[Squad10]

Use a sound activated relay device. It sounds like the FM transmitter you are using does not have PTT (Push To Talk) control, so the only way to control the FM transmitter is to power it up and down using the its cigarette lighter plug You can use the sound activated relay to supply power to the FM transmitters cigarette lighter plug. Route the 12v source through the switched side of the Normally Open relay contact, and connect the center pin of the cigarette lighter plug to the othetr side of the relay switch and away you go. How fast the sound activated device detects audio and the transmitter turn on time for full power/on freq.will dictate how much of the beginning audio is clipped or not.

If you are not understand what I am proposing or are not comfortable doing this yourself, ask someone who is to do it for you.

 

[Squad10]

Here's a link to a sound activated relay device.

Sound Voice Activated Relay Switch