Security & Saftey

Pull Pin Security Alarm System

The Pull Pin Security Alarm serves as a vigilant tool, ensuring that we receive immediate alerts in the event of someone attempting to pilfer our pockets or bags. This circuit is highly effective in thwarting pickpocketing attempts and has earned its name, the “Pull Pin Security Alarm System,” due to its activation upon the pin being pulled.

Here’s how they typically work:

Device Design:

  • The alarm device is usually compact and can be easily carried in a pocket, purse, or attached to a keychain. It features a prominent pull pin or cord that is connected to the device.


  • In case of an emergency or when the user feels threatened, they can quickly and forcefully pull the pin or cord from the alarm device. This action triggers the alarm.

Loud Alarm:

  • Once activated, the device emits a loud and attention-grabbing alarm sound, typically in the range of 100 decibels or more. The loud noise serves two primary purposes: to scare off potential attackers or threats and to alert people in the vicinity that there is an emergency situation.

Visual Indicators:

  • Some pull pin alarms may also include flashing LED lights or other visual indicators to attract more attention.


  • In some cases, the alarm can be turned off by reinserting the pulled pin or cord. However, this may vary depending on the specific design of the device.

Pull Pin Security Alarm Systems are often used in various contexts, including:

Personal Safety:

  • Individuals, particularly those who may feel vulnerable in certain situations, such as joggers, students, or late-night workers, carry these alarms to deter potential attackers and call for help.

Elderly and Vulnerable Individuals:

  • These alarms are useful for seniors or individuals with disabilities who may need immediate assistance in case of a fall or other emergency.

Campus Safety:

  • Some schools, colleges, and universities provide students and staff with pull pin alarms as part of their campus safety measures.

Workplace Safety:

  • In some workplaces, employees are issued pull pin alarms for personal safety, especially in situations where they work alone or during late-night shifts.

Travel Security:

  • Travelers may carry pull pin alarms for added security while in unfamiliar locations.


  • Pull Pin Security Alarm System Diagram:
  • Components Required:
  • Description:

Pull Pin Security Alarm Circuit Diagram:

Pull Pin Security Alarm

Components Required:

  • LM380
  • Resistor 1k -3
  • Capacitor 0.1uF-4,250uf-1
  • Speaker-1


The setup of this circuit is as follows: a pin is attached to the wallet, with one end connected to the circuit. The circuit remains dormant while the wallet is inside your pocket but becomes active when the wallet is removed.

As long as the wallet is in your pocket, the pin remains connected to the circuit, keeping it in an inactive state. However, when you take the wallet out of your pocket, the pin disconnects from the circuit, triggering its activation. When activated, a small loudspeaker is turned on, emitting an alternating audio frequency signal. This signal causes the loudspeaker to vibrate at an audible frequency, making it clearly audible to us.

This system can also be employed to safeguard other belongings such as purses, bags, and various items. Its applications are not limited to these scenarios and can be extended to other situations as needed. The circuit is designed to be compact and portable for easy carrying and operates on battery power.

The core component of the circuit is the oscillator, responsible for generating a sine wave of a specific frequency. It utilizes an RC phase shift oscillator, which produces a sine wave with the desired frequency. Each stage of the resistor-capacitor (RC) network consists of a 1 K-ohm resistor and a 0.1uF capacitor. These stages theoretically provide a 90-degree phase shift, but in practice, they contribute less. With three similar RC stages, each supplying approximately 60 degrees of phase shift, the cumulative phase shift becomes around 180 degrees. The amplifier circuit adds an additional 180 degrees of phase shift. Therefore, the total phase shift in the loop sums up to 360 degrees, a crucial criterion in the Barkhausen criteria for the circuit to function as an oscillator.

The circuit requires a 6V power supply, and the output is connected to a small loudspeaker with an internal resistance of approximately 8 ohms. When the circuit is activated, the audio oscillator’s signal is transmitted to the small loudspeaker, producing a beep sound at the specified audio frequency.


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