gey@ihlpl.att.com (Gerald E Yingling) (10/26/89)
I have a question about hooking up a cellular phone. First the problem. My wife bought a transporter car phone that has a cigarette lighter plug for "in car" use. Most of the time she keeps it plugged into her cigarette lighter, however, apparently there is enough drain on the car battery that if she does not use the car for several days and forgets to unplug the phone, the car battery goes dead. I think this is the problem: The cigarette plug is wired this way: ---------------------- < o o o o | "Molex" type plug ---------------------- | | | NC |----- | | ^ | | jumper | + - to cigarette lighter plug Note only two wires from car battery to the phone. I think this is the way a "permanent" phone would be hooked up: o o o o | | | | | | ignition | | switch | | | | | + + - car battery I believe two sources of power are needed, one unswitched (hot all the time) to keep the electronic lock active and some minimum reset circuitry alive, and a switched source (from ignitition switch) to provide transmit power. This would prevent battery going dead with the "cigarette" lighter approach. This might account for the jumper in the cigarette lighter/phone plug (first diagram). I would like to wire a new plug in the car so that my wife could unplug it, plug in the "internal" battery and have a portable phone. However before I messed around with this, I thought I would tap the expertise of the net and solicit advice. Assuming my assumptions are correct about two power sources, I'm not sure which terminal is switched and which is not switched (without trying and risking damage?). I traced the battery polarity so that is not a problem. The phone is a GE CF1000. Thanks for any help. Jerry Yingling 312-979-1639