A home security system can be invaluable when it comes to protecting your valuables (and even your safety!)

One of the main components of a circuit is to trigger your security system to activate an alarm. This alarm can either scare off a would-be intruder, or alert the authorities that something has gone awry in your home. Electronics Hub documents the pieces that make up a circuit, but if you’d like to make your own Circuit Digest has an in-depth tutorial that can aid in your project.

To learn more about how home security systems can benefit your house, check out the Protect America blog here!

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The Components

  • Resistor
  • R1, R2 (100K), R3 (1.2K), R4 (47E)
  • T1 (BC547), T2 (BC558)
  • D1, D2 (1N4007)
  • C1 (.1uf)
  • S1, S2
  • Speaker

The Breakdown


Resistors have two terminals, and they are passive. They are used primarily in the circuit to restrict or reduce the flow of the current across one of the circuits. The current that flows from the resistor is directly related to the voltage that comes across the terminals of the resistor. Resistors are mainly categorized into two groups:

  • Fixed resistor – This is a resistor whose values cannot be changed, and whatever is marked on it will be what it’s output is.
  • Variable resistor- The value of the resistance that this resistor can handle can vary within a set range. The value range will be marked on the resistor, either with a scale or with an industry-standard color code.


These asymmetric attribute devices have two terminals. They allow the flow of a current in one direction, while the flow of high resistance comes from another. The flow of the current is one-way only. The two terminals are named anode and cathode, and they are used to convert an AC current into a DC current.

Want to learn more about how to wire your own home security system? Check out our blog post on it here!


This electronic device has three terminals, which are used to amplify weak signals. Traditionally used in electrical appliances because they are small and lightweight, transistors posse less power, which makes them more efficient. These devices usually consist of two junction diodes connected together back to back. Types include bipolar junction, field effect, and phototransistor. 


A device that creates sound in response to the electrical signal given to the input from the circuit action.


Electric charges are stored by the two terminal parts, which are (by nature) passive. A dielectric (or two) medium is used to separate the conductors, which in turn helps to cut down on potential variations that can occur in the ions of the charge. The two main varieties of capacitors are:

  • Polarized capacitor: These devices are marked with both negative (-) and positive (+) signs. They are used to hold the overall charge. (There is a chance of shocking yourself if you don’t discharge them before handling.)
  • Non-polarized capacitor: These capacitors do not have any polarity marked on them (or no – or + signs.) These are used to cut down or remove the noises that occur when AC is converted into DC.

How It Works

The two S switches can be put in different places to create different paths. When either of the S switches are pressed, it presses D1 (or the diode), which will jumpstart the transistors (the T1 and T2). This begins the conduction. Transistors T1 and T2 get positive feedback (or current), which is provided by C1 (or the capacitor). A low tone frequency would be generated when the switch was pressed.


Basically, when the S switch is triggered, it sets off a chain reaction that in happens very quickly. The reaction goes through each of the pieces, setting off and triggering the next phase. At the end, a frequency is made, or a sound, which would then trigger your alarm system to make a even louder noise through a built-in speaker. Additionally, some of the circuits would trigger an alarm call, instead of a sound.

Does all of this sound too complicated to build yourself? Have no fear: You can protect your home and valuables by trusting the professionals at Protect America today!