Looking for an alarm system to alert you to others crossing your property? You can purchase one inexpensively at Harbor Freight which works well and is easy to set up. Larger property owners should purchase several units to full get coverage. Each unit comes with a sender and receiver with a channel identifier shown on the box. There is one alert tone regardless of the channel being tripped. This unit can use a 6 volt, 200 mA power adapter but the manufacturer doesn’t sell one. The system is a good buy for those wanting an audible alert for their property.

Key Takeaways:

• To offer some further information, each box contains one sender and one receiver. Each box has a small oval sticker on the front identifying the channel. All of my units utilize the same tone.
• The receiver can utilize an optional 6 volt, 200 mA power adapter, but the manufacture doesn’t offer it for sale.
• This will hopefully give me a heads up when someone is approaching the house. One final note: The receiver unit has a visible red indicator light.

“The receiver unit has a visible red indicator light. If you are concerned about someone seeing this while they are “casing the joint” you may want to cover it with black tape.”

https://survivalblog.com/letter-re-inexpensive-perimeter-security-for-your-house-in-the-suburbs/