Telephone Guard. Simple Design 24

This simple add on circuit prevents misuse of Land Phone and also indicates whether the Phone lines are Ok or not .It is an ideal tool to test the Telephone lines. It lights LEDs to confirm the signals coming in the Telephone lines. It can also be used as a simple Telephone lock to block outgoing calls.

Telephone Line Monitor. Beginner’s Trial 12

This simple circuit performs multi function. It always monitor the Telephone lines and see whether there is any misuse and gives LED indication if it occurs. It gives indications like Phone ON hook state, Off hook state, dialing etc. It is ideal as a tester to see whether the lines are available or not , modem in use etc. It needs no external power and uses the voltage from telephone lines. Two LEDs and a single resistor will make this circuit. You can fix it in the telephone junction box. Make and invite your friends to see your work.