AUDIO-VISUAL EXTRA RINGER FOR PHONE
Many a times one needs an extra telephone ringer in an adjoining room to know if there is an incoming call. For example, if...
SONG NUMBER DISPLAY
Here’s a circuit to display the song number in an audio system for quick reference to songs. It also serves the purpose of an...
ELECTRONICS CARD-LOCK SYSTEM
The circuit presented here can be used as a lock for important electronic/electrical appliances.
When card is inserted inside its mechanism, depending upon the position...
DARK ROOM TIMER
The timer circuit described here provides a pleasant musical tone in your darkroom at 1-second intervals.The circuit takes up very little space and can...
Electronic Horn
Here’s a simple circuit of an electronic horn that is built around quadruple op-amp IC LM3900 (IC1). IC LM3900 has four independent op-amps (A1...
Teleremote Control
Here is a teleremote circuit which enables switching ‘on’ and ‘off’ of appliances through telephone lines. It can be used to switch appliances from...
SLEEP SWITCH CUM WAKE TIMER
Here is a sleep-switch circuit that can be easily converted into a wake-up timer. A dual-mode time setting makes the system versatile. The circuit...
CORDLESS PHONE BACKUP
Normally the base of a cordless phone has an adaptor and the handset has Ni-Cd cells for its operation. The base unit becomes inoperative...
PRECISION DIGITAL AC POWER CONTROLLER
Triacs and SCRs are extensively used in modern electronic power controllers—in which power is controlled by means of phase-angle variation of the conduction period....
Handy Zener Diode Tester
Here is a handy zener diode tester which tests zener diodes with breakdown voltages extending up to 120 volts. The main advantage of this...
