Cell-Phone 101 info requested.

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Well-known member
Sep 1, 2006
Florida, USA
  I am using a small simple phone - Tracfone- and rarely have it turned on in the receive mode. Only my DW  an AAA has my number.

Here is my question:  Today I had reasons to have it turned on waiting for a call from MY DW after a short hospital visit, so that I could retrieve her from the hospital door. I was parked , listening to the radio, a long distance away from the hospital door.  Yes, the phone started to ring and I retrieved her as planned.

Now to the question:  I had the phone lying on the dashboard for easy access. Just before the ring sounded, the radio on AM produced a pop and then muted totally. I thought 'nice feature' but but it surprised me, being a radio nut. I suppose that when a cell tower signal contacts the phone it wakes it up and forces it to send a relatively strong transmitted signal back. Strong enough to saturate the car radio???

Is this normal?  It happened once before, tuned to an FM radio station ..same thing.

I suppose more info is required to solve this puzzle. Ask away.

  Remember, this is not an emergency call for help.    ;D

The phone begins transmitting, intermittently, shortly before it plays the ring tone.  The transmissions can disrupt nearby electronics (especially cheaply made, badly shielded electronics) in various ways.  That it worked to your benefit in this case was due to serendipity rather than design.

Thanks Jammer,  that makes sense. I don't know what shielding is involved in the $130.00 radio -Pioneer-

Serendipity - perhaps you had something to do with that with your screen name.  ;D

If you use an "Aux" device such as an MP3 player and the phone is near the cable connecting it to your radio, or if you use a headset device, you can often hear the phone chat with the tower (They handshake every so often) as you move about.

When the tower sent the "RING" signal, the phone sent back "OK" Some top end radios sense the activation of the cell phone and do as you described... How it knows the difference between "Hello, Here I am" and "Ok, I'm ringing" I do not know. but that's beacuse I don't know the cell protocol, it is easy to tell 'em apart if you know 'em.

In the old days... When we had bag phones, it was possible to sense current and shut down, those too ignored the "Hello" packets, but tripped on an answer/dial packet.
Thanks, John.  That makes sense too. Maybe there is something in the radio manual about that. I am not a very good manual peruser, usually only read them when I get into trouble,  ;D

In the mid to late 90's I used a bag phone - and ususally left it on the console between the captains chairs. When a call was coming in while playing the TV - the TV sound would stop. The sound would go dead, then the phone would ring.

After that I had fun with it. If I had company and we were watching TV I would have the remote beside me. If the sound would stop, I would quickly pick up the remote and act as though I had just turned down the sound. And then announce to my guests to excuse me because a call was about to come in -- then the phone would ring. When asked how I knew, I would explain that I really didn't know, I just "sensed" it somehow.  :)
carson said:
Thanks Jammer,  that makes sense. I don't know what shielding is involved in the $130.00 radio -Pioneer-

Serendipity - perhaps you had something to do with that with your screen name.  ;D

Absolutely, Carson.  Always part of the noise, never part of the signal. :D  But then again, internet forums and broadcast television share the property that the noise is sometimes more interesting than the signal.


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