Masterdation Encouregement

When several people have access to the same telephone line and each has its own device, it often happens that when you lift the handset to make a call realizes he is being used by another person.

To prevent this discomfort is advisable to install a device to indicate when the phone line is being used by another person. The indicating device is a small circuit that connects to the telephone line (in parallel with the phone).

This circuit contains two LEDs, one blue indicating that online is free and green indicating that the line is busy. This circuit requires no external power and telephone lines that have an alternating voltage to pass through the bridge rectifier eliminate the negative side, so we can use transistors when the voltage is below a set range, the corresponding LED is activated.

Used Components:

- 1 blue LED.
- 1 green LED.
- 4 1N4007 diodes.
- 2 Transistors 2N3904.
- 1 33K ohm resistor 1 / 2 Watt.
- 1 resistance 3.3K Ohm 1 / 2 Watt.
- 1 56K ohm resistor 1 / 2 Watt.
- 1 Ohm Resistance de22K 1 / 2 Watt.
- 1 resistance 4.7K Ohm 1 / 2 Watt.