576924 @rewrew Yes online ordering is better if you want multiple PCB's all the same, but what if you just want a 1 off PCB as I regularly require? A 1 off PCB is a no go with online ordering, as it is not worth their while.

576924 It clearly states in the diagram above where to connect the antenna wire.

576924 It clearly states in the diagram above where the antenna wire is connected.

576924 Where can I obtain the datasheet for the HC12?

576924 Just use a test meter and measure the resistance between the two outer pins on underside of board. It is probably 10k, and will have 103 stamped on case. This means 10 to the power of 3 = 10K. Yes I myself have removed the onboard variable resistance, and replaced it with an off board one with control knob and leads connected to the PCB. Works satisfactory, although it would validate any warranty with the project, however as you can see they are priced very cheap.

576924 It would be a simple mater to add either a PIR, or M/wave sensor across the bell push for automatic sensing. This would of course render any warranty tht came with the unit.

576924 You need to connect an aerial to it capable of handling 5 watts. Operating it without an aerial means there is no way for the energy generated by the transmitter to be dissipated. It is therefore dissipating that unused energy directly into the unit itself causing it to get hot. This will eventually damage the unit over time, so do not operate without an adequately matched 50 ohm impedance aerial.

576924 Size: 46mm x 40mm It's in the Specification