@▷ One Time Alarm Circuit Schematic Diagram | Diagram for Schematic

One Time Alarm Circuit Schematic Diagram

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 switch off and remain off. The alarm will not re-activate.

The basic circuit has a single zone with independently adjustable Exit and Entry delays. The zone will accommodate the usual types of normally-open and normally-closed input devices – such as pressure mats, magnetic-reed contacts, micro switches, foil tape and PIRs.




one-time-alarm

The alarm may be operated by a simple hidden two-way switch – such as a light switch. If you want more security – you can use a key switch – or one of a number of code operated Keypad Switches.

Before you set the alarm – make sure that the building is secure – that ALL of the Green LEDs are lighting – and that the Yellow LED is off. If the Yellow LED is lighting – there’s a fault in one of the zones – and THE ALARM WILL NOT SET.

Depending on the setting of R9 – when you move Sw1 to the “set” position – you have up to about a minute to leave the building. When you return and open the door – the Buzzer will sound. Depending on the setting of R8 – you have up to about a minute to switch the alarm off. If you fail to do so – the Siren will sound.

Depending on the setting of R14 – the Siren will sound for up to about 20-minutes. Then it will switch off – and remain off. Of course – you can stop the noise at any time by moving Sw1 to the “off” position.

When you return – if the Buzzer does not sound and the Yellow LED is lighting – then there’s been an activation while you were away.

source : zen’s circuit diagram

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