I want to check for the presence of a tag by phone. I thought of an audio buzzer that i can simply hear when i call in with auto answer, but normal sound is just too unreliable and somewhat annoying.

Could there be some kind of rf tag that i can detect through the normal phone 3.5mm jack? Not using extra battery that would only run out quickly, just the supplied voltage from the jack.

Thanks, I know there must be a solution, just cant think of it

 

i thought of an induction coil and then have a tag that pulses so that it gets picked up by the coil? The tage can have a battery, but it needs to last long

 

Can you elaborate on what you mean by a tag?

A tone is emitted by a smart phone in the presence of an ID tag?
How close do you have to be to the tag?

 

a small tag/beacon/send thingy, like a few cm2, with a button cell battery.

the tag would be within a few meters.

Basically, what kind of sensors can you connect to a headphone jack, so that it detects RF instead of a voice.. The inductive coil (like those hearing aids) with a tag that create RF, could that work?

Inductive coil is normally used to send to a tiny earpiece. I would want to use it to receive RF, not sure if that would work.

thanks

 

What's wrong with using Bluetooth?

 

a small tag/beacon/send thingy, like a few cm2, with a button cell battery.

the tag would be within a few meters.

Basically, what kind of sensors can you connect to a headphone jack, so that it detects RF instead of a voice.. The inductive coil (like those hearing aids) with a tag that create RF, could that work?

Inductive coil is normally used to send to a tiny earpiece. I would want to use it to receive RF, not sure if that would work.

thanks

No sensors connect to the headphone jack.
You connect earbuds or headsets to the jack, usually about 8Ω to 32Ω impedance. Audio frequency signals are output on the jack, not RF.

 

No sensors connect to the headphone jack.
You connect earbuds or headsets to the jack, usually about 8Ω to 32Ω impedance. Audio frequency signals are output on the jack, not RF.

I thought maybe as a hack there would be other sensors that could be connected in place.

Bluetooth BLE is ideal, but not sure how i can receive the signal by calling in remotely on the phone?

 

I'm not sure what you're trying to achieve, is it different from this kind of thing:
http://www.hongkiat.com/blog/bluetooth-tracking-devices/