Subscribe by RSS feediPhone FM transmitter keep-alive
On the recommendation of a colleague, a friend and I picked up super-cheap iPhone FM transmitters from a dodgy stall in our local shopping centre. It only cost a fraction of a poofteenth of what you’d pay for a real FM transmitter, and this colleague had not had any troubles with it.
My friend’s one, too, works fine to this day, but I quickly found a problem with mine. While driving around in the car, listening to my iPhone on the stereo, as soon as I hit a bump, the music would disappear to be replaced by a static-covered elderly gentleman quietly talking about God. I figured the accessory was being jiggled and this was causing an interruption of power to the transmitter, which subsequently switched off. I tried using rubber bands to keep it in place, with no luck.
Today, I decided to sort this matter out. It wasn’t a significant expense, but it would be nice to have it working, so I started doing some tests. The result was very interesting – bumping the phone around was not the cause, because even if I was stationary, after a time the music would stop. Moreover, it would always happen pretty close to one minute after plugging in the device.
My conclusion, then, is this. iPhone 3G accessories send keep-alive signals to the phone every 60 seconds saying, “Hey, don’t forget about me, I’m still hanging out your socket”, and the phone therefore continues to supply power and the appropriate data to the device. For reasons unknown, my defective FM transmitter doesn’t send these signals, and so after the phone doesn’t hear from it for a minute, it just assumes it’s no longer there and cuts the power.
So I now understand the problem, but I’m not very much closer to a solution. The dodgy stall disappeared within a few days (of course) and this device doesn’t have any manufacturer’s name on it, so I’m kind of stuck with it. Maybe I’ll find a solution.. next year.
