Voltage
The previous sections explain how electrons move and that they move more freely in a conductor. But some kind of force has to pull the electrons from one place to another. This attractive force between positive and negative charges is an electromotive force called voltage. Negative electrons move toward a positive voltage by way of a conductor.
Remember Ben Franklin’s adventure flying a kite in a storm? The spark he produced that night gave him an understanding of how an electric current moves. In Ben’s case, electrons travelled down the wet string, which acted as a conductor. (This was at least in part because the string was wet. Try this same stunt with dry string and it doesn’t work as well). The voltage difference between the negatively charged clouds and the ground pulled the electrons down the wet string.
The electrical force that moves electrons through a conductor.
- Represented by the symbol V
- It is measured in Volts
- AC input voltage can be 16Vac to 18Vac, depennding on the manufacturer of the alarm system.
- Alarm systems uses 13.5 to 13.7Vdc – Supplied from the panel to sensor devices
- Note when AC fails this Voltage can go as low as 10.5Vdc
- 10.5Vdc is the cutoff voltage for the battery – This is to protect the

The system also includes a battery terminal responsible for charging batteries and supplying power during an outage. The battery connector provides a DC voltage that charge the batteries and use the battery in case of a power failure. This terminal is used to charge batteries only. The AC is the 16Vac voltage source that powers the panel, and the AUX terminal is a DC voltage output terminal used to power peripherals.

We use the 13.7Vdc to supply power to sensors devices and power modules on the system. The supply voltage is called Aux output (AUX+/AUX-) on PCBs. The output is limited in its supply, and is also regulated, meaning that the voltage under normal operating conditions will be stable. It’s important that we connect the terminals correctly here, since they have a dedicated + (positive) terminal and – (negative) terminal. Although the output on most panels are protected against short circuits and swapped polarity, not all equipment is equal in this regard.
Most older systems make use of a fuse to protect the circuit, and if you blow the fuse do not replace it with anything that is not designed or rated for the holder slot. If your fuse blows look for a similar rated fuse. it is essential to replace it with a one that matches the original design and rating for the holder slot. Do not use anything else like soldering wire, aluminium paper, electrical cable