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From the Technology Enhancement Programme (TEP), these circuits allow students to build a range of devices. Each circuit has a full circuit diagram, component list and explanation of how the circuit works. In this section, the circuits cover a range of security devices.

A mousetrap (light)
When the mouse breaks the infra-red beam, a motor switches on, closes a door thus trapping the mouse without causing it any physical harm.

Bath level indicator
As the water rises in the bath, four LEDs will switch on in sequence to indicate the water level.

Cupboard alarm
When a cupboard door is opened, a lamp will light for a pre-determined time. An advantage of this circuit being that when in the stand-by mode the circuit consumes no current, thus the battery life is prolonged.

Cat flap
A circuit to inform whether the cat is in the house or not.

Trailer indicators
A circuit used to indicate in which direction the driver is turning the vehicle.

Flashing badge
This circuit produces a flashing display.

Bicycle alarm
In this circuit, when a wire loop is cut a buzzer sounds and continues to do so until the circuit is switched off.

Intruder alarm
In the event of either of the two sensors being activated, a buzzer will sound and continue to do so until switched off.

House protection
In the event of any of the sensors being activated, a buzzer sounds and remains active until the circuit is switched off.

Micro-switch alarm
A push-to-break switch is held open by an object placed on top of it. When the object is removed, the switch will close and a buzzer will sound until reset.

Toolbox protection
When the lid of a toolbox is raised, an LED will flash and a buzzer will sound.

Personal alarm
When the circuit is activated and a push to break switch is pressed, the alarm will emit a shrill note.

Rotary lock
When the settings of three rotary switches are in the correct position, a solenoid is activated.

Keypad lock
When the correct sequence of switches are pressed, a motor rotates (or a solenoid is activated) to unlock a door.

Intercom (baby warning)
A one way listening system.

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