DX 433Mhz Wireless Door Contact 248919
This is based on a EV1527 encoder and therefore works with RCSwitch. They're detected as 24-bit, protocol 1, no Tri-State. Pulse length varies between about 347 and 350 microseconds.
The two devices I have report their id's as;
Alarm Sensor: 13857492 110100110111001011010100 Alarm Sensor: 9373908 100011110000100011010100
Device is a pretty simple reed switch with a magnet, normally closed and triggered when the connection is broken, this should be easy to hack to other usage. With the magnet in range and the reed switch closed, nothing is transmitted. Once the connection is broken, a blue LED is activated for a couple of seconds and the unit transmits it's code. It seems to repeat 9 or 10 times. It resets as soon as the magnet is brought back in range, it should easily detect any quick opening of the door/window.
There's a fair amount of spare space in the case for adding additional circuitry - I'm thinking a transistor to reverse the functioning of the circuit and use this as a simple trigger circuit for a doorbell, these are much cheaper than the cheapest wireless doorbells.
Soldering looks fine, generally well made but there's no antenna on the board which seems to be massively limiting their range. There's a through-hole space for one to be added, 17.2cm of wire should do the trick.
Aside from the EV1527 there's also a HEF4011BT which according to the datasheet is a quadruple 2-input NAND gate. Perhaps it won't be necessary to mess about with a transistor after-all, perhaps this can be hacked even more easily...
Affiliate link to DealExtreme: http://dx.com/p/248919?Utm_rid=65939668&Utm_source=affiliate