T&L Publications

I'm trying to figure out how to build a circuit, It will 'splice' the audio from my cell phone's 'ear bud' audio into my walkman's left (or both?) ear audio. I will hang the mic seperately. <p>What I would *like* is that if audio is present from the cell phone (ie, I'm on or getting a call) that the audio from the headphones is faded completely down. When the call ends (or the voltage in from the audio out = 0) the music volume would return to normal.
I'm sure this can be done just haning trouble finding the circuit diagram. Any takers? TIA!!

I posted a schematic at the URL below. I have not built it, so no guarentee. If you build it and have a problem, feel free to email me.
http://www.geocities.com/russlk/sigsw.jpg<p>NOTE: you have to copy and paste the URL because geocities does not allow links.<p>[ February 26, 2003: Message edited by: Russ Kincaid ]</p>

Thanks Russ! I will give it a shot and reply results! Anything I should know component wise? TA!

Does your cell phone's ring sound over the earphone? Both my phones don't do that, just something to think about.

My phone doesnt ring in the earpeace per se. It does however make a slight click and then a hollowish, faint white noise sound even before the phone rings itself. I have yet to test the levels on it. What are the thresholds of this circuit?<p>Also, could someone point me to a good place for the DG419? It seems DigiKey only has them in 100pc where they have the TLC372 in singles.<p>I'm also curious if there is a variant of the DG419 to emulate DPDT? I would like to mute both (LR) channels of my headphones yet only have the one ear (L) come on for a phone call. I presume I could just include a second DG419 in the circuit Russ provided(?).<p>[ February 27, 2003: Message edited by: Costa ]</p>

I had an early Panasonic phone that used the earphone as the ringer. I can't hear that frequency any more!<p>I will look into using a quad switch instead of the DG419.
You ask about sensitivity; it is too sensitive, I need to put some hysterises in the comparator. About 100 mV should do it.<p>[ February 27, 2003: Message edited by: Russ Kincaid ]</p>

I have posted a new schematic using a quad switch, and have corrected some errors in the original schematic. I did not use hysteresis, I used a 100 mV offset instead.<p>Don't forget: you have to copy and paste the URL.
http://www.geocities.com/russlk/sigsw.jpg<p>Oops! I had the switch backward, the correct schematic is now posted.<p>[ February 28, 2003: Message edited by: Russ Kincaid ]</p>

Thanks Russ!