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Relay protection circuit – Circuit Schematic
Relay protection circuit
Operating power protection devices, there is a DC power supply operating power and AC operation into two categories. ...
Automatic distress alarm kit control circuit – Circuit Schematic
Automatic distress alarm kit control circuit
Circuit works: When the patient usually upright, packed in kit SQ mercury switch was turned off,...
Automatic distress alarm kit control circuit – Circuit Schematic
Automatic distress alarm kit control circuit
Circuit works: When the patient usually upright, packed in kit SQ mercury switch was turned off,...
High Voltage Ringer – Circuit Schematic
High Voltage Ringer
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You Have Mail! – Circuit Schematic
You Have Mail!
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Ultrasonic RepellentCircuit! – Circuit Schematic
Ultrasonic RepellentCircuit!
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fake car alarm 555 led flash schematic – Circuit Schematic
fake car alarm 555 led flash schematic
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Midnight Security Light Circuit Schematic – Circuit Schematic
Midnight Security Light Circuit Schematic
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You Have Mail! – Circuit Schematic
You Have Mail!
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security camera – Circuit Schematic
security camera
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Universal Four-Digit Keypad-Operated Switch - Construction Details – Circuit Schematic
Universal Four-Digit Keypad-Operated Switch - Construction Details
The key you`ve connected to "E" is used to energize the relay. And the four keys you`ve connected to A, B, C & D - are used to de-energize it. All the other key...
Two-Zone Alarm – Circuit Schematic
Two-Zone Alarm
This is a two-zone alarm - with automatic exit, entry and siren cut-off timers. It can be triggered by the usual types of normally-closed input devices - such a...
Transistor Based Burglar Alarm - Adding Extra Zones – Circuit Schematic
Transistor Based Burglar Alarm - Adding Extra Zones
You can add as many extra zones as you like to the Transistor Burglar Alarm System. The first circuit is designed to be used with the usual types of normally-cl...
Enhanced Alarm – Circuit Schematic
Enhanced Alarm
This is an enhanced version of the simple Garage/Shed Alarm. The Entry and Exit delays have been increased to about 30-seconds - and I`ve added a timed Siren cu...
Automatic Garage / Shed Alarm – Circuit Schematic
Automatic Garage / Shed Alarm
This is a simple single-zone burglar alarm. The basic design includes automatic Exit and Entry delays. It doesn`t include a siren cut-off timer. But with A Smal...
An SCR Based Burglar Alarm - Adding Extra Zones – Circuit Schematic
An SCR Based Burglar Alarm - Adding Extra Zones
You can add as many extra zones as you like to the SCR Burglar Alarm System. The first circuit is designed to be used with the usual types of normally-closed in...
An SCR Based Burglar Alarm – Circuit Schematic
An SCR Based Burglar Alarm
This is a simple SCR based burglar alarm circuit. Its features include automatic Exit and Entry delays - together with a timed Bell cut-off and Reset. It`s desi...
A Simple Keypad-Operated Switch - with enhanced security – Circuit Schematic
A Simple Keypad-Operated Switch - with enhanced security
This is a universal four-digit keypad-operated switch - with a difference. Instead of entering the security code one number at a time - the four keypad buttons ...
How To Build A One-Time-Only >> Burglar Alarm Circuit – Circuit Schematic
How To Build A One-Time-Only >> Burglar Alarm Circuit
This alarm is designed to sound its Siren only once. That is - when the alarm is activated - the Siren will sound for a preset length of time. Then it will swit...
A Dozen Small Battery-Powered Alarm Projects – Circuit Schematic
A Dozen Small Battery-Powered Alarm Projects
This is a selection of small self-contained alarm circuits. The main features of each alarm are described on the circuit diagram itself. They all have a very lo...