FM Telephone Bug


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Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range is about 200 feet. It is extremely easy to build and is therefore a good, useful beginner project.

Schematic

This is the schematic of the phone transmitter

Parts

Part
Total Qty.
Description
Substitutions
R11180 Ohm 1/4 W Resistor
R2112K 1/4 W Resistor
C11330pF Capacitor
C2112pF Capacitor
C31471pF Capacitor
C4122pF Capacitor
Q112SA933 Transistor
D1, D2, D3, D441SS119 Silicon Diode
D51Red LED
S11SPDT Switch
L11Tuning Coil
MISC1Wire, Circuit Board

Notes

  1. L1 is 7 turns of 22 AWG wire wound on a 9/64 drill bit. You may need to experiment with the number of turns.
  2. By stretching and compressing the coils of L1, you can change the frequency of the transmitter. The min frequency is about 88 Mhz, while the max frequency is around 94 Mhz.
  3. The green wire from the phone line goes to IN1. The red wire from the phone line goes to IN2. The green wire from OUT1 goes to the phone(s), as well as the red wire from OUT2.
  4. The antenna is a piece of thin (22 AWG) wire about 5 inches long.
  5. All capacitors are rated for 250V or greater.
  6. The transmitter is powered by the phone line and is on only when the phone is in use. S1 can be used to turn the transmitter off if it is not needed.
  7. If you have problems with the LED burning out, then add a 300 ohm 1/4W resistor in series with it.

Related Circuits

Ringing Phone Light Flasher, Phone Busy Indicator, FM Telephone Bug, Cut Phone Line Detector, Simple Phone Tap, Telephone Hold Button, Telephone Recorder, Remote Telephone Ringer

Comments

dharmendra chauhan
FM Telephone Bug
Wednesday, October 22, 2008 2:49:40 AM
it is good for me...........i foud this type of project such a long time..........i need a hoby project for my EDC,..plz send me this kind pjt on my mail... thank u
Ravish
FM Telephone Bug
Wednesday, October 15, 2008 2:02:12 PM
Thanks for giving this wonderful circuit....... Will you please explain this circuit properly & how could i extend the range???? And one wonderful thing i found is that we can use 1N4007 diodes in place of 1SS119...
Gaz
FM Telephone Bug
Thursday, September 11, 2008 7:05:53 PM
Please can you advise me on where to buy 1SS119 Silicon Diodes, Thanks!
getnet zewde
FM Telephone Bug
Saturday, August 23, 2008 4:02:30 AM
thise ckt is legale no probelemfor tell
anonymous
FM Telephone Bug
Tuesday, June 10, 2008 10:27:14 AM
We are interested in ding this project can you please help us how do we connect circuit to the phone line becouse we have two inputs and two outputs.
swadjaya
FM Telephone Bug
Sunday, June 01, 2008 4:38:02 AM
I need information about 1SS119 Silicon Diode substitution because I can't find this item in Indonesia. Thank's
keanhong2
FM Telephone Bug
Monday, May 05, 2008 11:11:04 AM
question 1)the diode 1ss119 silicon diode can replace wait what other similar to these diode ? 2)transistor 2sa933 got other replacement ??
crrimson
FM Telephone Bug - Circuit works!
Monday, April 28, 2008 11:47:25 PM
This is the first FM transmitter I've gotten to work, and it was pretty easy to build, it works great! Thank you. For anyone trying to build it, I used a BC557 transistor for Q1, and 1N4002 for D1-D4 instead since I couldn't find the parts it asked for.
Kyle
FM Telephone Bug
Tuesday, April 22, 2008 12:03:52 PM
Where can I buy a 1SS119 Silicon Transistor? Or is there something else that can be substituted? Thanks!
anonymous
FM Telephone Bug
Monday, April 07, 2008 12:04:06 PM
Is there a circuit that can be used to detect this bug or any other bug for that matter? If there is, can you please send it to me together with its description.
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