Off-Hook Telephone Line Indicator

The circuit is designed to connect in parallel with the telephone line, to monitor and detect if any telephone in the same line is busy, with the indication of the LED and which is self-powered so that it does not provide any load on a telephone line.

Electronically Designed Keypad

The circuit was designed to function as an electronic keyboard using CMOS 4081 integrated circuit.

Electrically Operated Siren by 2N3702 and BC108B

The circuit was designed with just one circuit element wherein the tone of the siren varies with the actions of a push button switch.

Building a Passive Ethernet Hub

The circuit illustrates the operation behind the design of a passive ethernet hub in connection to the signals being received and transmitted.

Fast Electronic Fuse

The function of this circuit is as an electronic fuse which cut the current off when it is exceeds certain limit. Time response is fast and the current limit is adjustable.

Magnetically Operated Gun by NE555 and 4017B

The circuit is designed to produce a gun using the technology of magnet to drive a minimal hit a long distance horizontally or a few distance vertically.