Hi and good day to you guys.
Thanks for the circuit diagrams you've all shared. I was looking at it and tried to come up with something like this. The purpose is to have a Modular Theft Alarm. The Tx should be emitting somewhere 4Khz with in 2ft radius. As long as the receiver, which is placed in a bag or any item valuable, receives the 4Khz it wont alarm. Incase a thief tries to take it away, once he gets 2ft from the owner where the transmitter is, it will sound off. Would this work? I would like to know also the right values of each capacitor to Transmit/Recieve 4Khz.

Help me come up also with a very high pitch alarm circuit with very minimal components.

thanks...much power to you all!

HI, that is a nice circuit you got there.
what I think is that you cange the 1-10micof cap to a
ajustible cap.

PS, dose the transmiter work.

Am not realy sure if it'll work. Havn't started the prototype yet. Still want to get more feedbacks from the experts I just had those circuits all together from this site and some other sites and tried to juggle some ideas. But thanks for the advise. I will try that and might start the prototype and do a lot of testing. Will be looking out for an osciliscope to rent out.

I have a program that might help you but it dosen't have transistors.
I will have to email it to you

Big thanks in advance Sir!

you can email me at

mailto:sgt.hksdriver0@mailcity.com

Did you get the email. Hey your e-mail is meesed up
I'll give you the web site were I got it from.

[www.mariucci.freeserve.co.uk]

Did you get the program? how is it?
I havn't figured out what those lines mean.
Sorry I don't have more anserws.

Dear sir, sorry for the very late reply. I got busy over the past weeks. The site is great sir! Thankyou very much! Will be pursuing the project again. Again thank you!

You don't have to call me sir I'm only 18.
The reason you see me loged in all the time is I don,t logout
becuse I forgot my password.
If you wanted to know.

Hi to all --
What has been requested is a TX (and relative RX) in the 4 KHz range !!
This is AUDIO range and the two TX circuits shown are RF, weeeeeellllllllll beyond the needed 4KHz.
Question: why settle for an audible frequency ??
4KHz is very audible and since earing is pretty much peaked at 3KHz, this tone will become quite pronunced and irritating. Unless THIS is the reason for the project ..
Cheers
- Angelo

The purpose of the circuit is a wirless alarm. Lets say you have a painting and you don't want anybody to take it, so you put the transmiter on the painting and hook the reciever to your burglar alarm. If they take it they'll set of the alarm.

And it so happen that the circuits i found are in the 4Khz range. Any frequency recomendable for such project with corresponding circuit diagram? Thanks in advance.

Andrew, yes you got the idea. Petty theft are so rampant nowadays. By the way, FYI am from the Philippines and age 26.

So did you get the program I told you about?
Dose it work the way you want it to?
How much range did you get with it?

I need a rf transmiter circuit to use with my encoder and a
reciever for the decoder.
A encoder and decoder will keep random signals from interfering.
The encoder and decoder I got from:[www.microchip.com]#
They need to be programed.

It's been awile since any one replied.
Any way did you get it to work.

I was thinking of using an Ic to control the transmitter circuit (pulse modulation), so is there a receiver that can put out a logic 1 when it is receiving the signal at the specific frequency, and a logic 0 when it isnt. also does anyone know what the effect of different values of components in the transmitter circuit will have on the frequency? thanks in advance

Hi all, I'm new to this site and new to the world of Electronics
Started reading the dummies guide and then needed something to start playing with. Figured a transmitter and receiver would be a good place to start.
Found this site and this pair of components for the modular burgular alarm. Built the transmitter and am only 2 components away from the receiver. Finally found the Transistor for the receiver will get it soon.
But I'm confused by the variable cap on the transmitter, does it have to be variable or can it be anywhere in the 30-200pF range. And where can I locate one of these?
Soon as I get these last 2 parts I'll put it together and let you guys know if I got it working. Then I'll start modifications to see if it's usable for RC control.
Again, I need to know more about the cap, please. Thanks