DIGITAL SWITCHING SYSTEM
This circuit can control any one out of 16 devices with the help of two push-to-on switches. An up/down counter acts as a master-controller...
COMPUTERISED MORSE CODE GENERATOR/TRANSMITTER
The circuit given here can be used to send telegraphic messages via computer. The message data entered through the computer keyboard is converted to...
UPS FOR CORDLESS TELEPHONES
Cordless telephones are very popular nowadays. But they have a major drawback, i.e. they cannot be operated during power failure. Therefore usually another ordinary...
Telephone Security Circuit to Prevent Unauthorised Line Use
Most of the telephone security devices available in market are simple but quite expensive. These devices provide blinking or beeping type line-tap misuse indications....
Intelligent Emergency Light Switch for Automatic Darkness Detection
This intelligent switch circuit enables automatic, switching on of an emergency light system during darkness in the event of mains failure. The mains power...
LOW CURRENT, HIGH VOLTAGE POWER SUPPLY
A high voltage power supply is a very useful source which can be effectively used in many applications like biasing of gas-discharge tubes and...
DIY Telephone Call Meter Using Calculator and Quartz Clock Circuit
In this circuit, a simple calculator, in conjunction with a COB (chip-onboard) from an analogue quartz clock, is used to make a telephone call...
Connect Two Telephones in Parallel Without Interference
Often a need arises for connection of two telephone instruments in parallel to one line. But it creates quite a few problems in their...
Automatic Room Power Controller
An ordinary automatic room power control circuit has only one light sensor. So when a person enters,the room it gets one pulse and the...
TELEPHONE RINGER USING TIMER ICS
Using modulated rectangular waves of different time periods, the circuit presented here produces ringing tones similar to those produced by a telephone.
The circuit requires...
