Wiring glossary
Plain-English explanations of common wiring diagram and low-voltage security terms.
What is PoE?
Power over Ethernet is a method of sending power and data over the same Ethernet cable, commonly used for CCTV cameras, intercoms and wireless access points.
What is an NVR?
A Network Video Recorder records video streams from IP cameras over a network.
What is a dry contact?
A dry contact is a relay contact that does not supply voltage by itself.
What is a relay output?
A relay output is a switched contact used to control or signal another circuit.
What is fail-safe vs fail-secure?
Fail-safe generally unlocks when power is removed, while fail-secure generally remains locked when power is removed.
What is Wiegand?
Wiegand is a legacy access control reader communication format using data lines such as D0 and D1.
What is OSDP?
OSDP is a reader communication protocol commonly used over RS-485 style wiring.
What is RS-485?
RS-485 is a serial communication standard commonly used for bus-connected field devices.
What is voltage drop?
Voltage drop is the reduction in voltage along a cable caused by cable resistance and current draw.
What is an EOL resistor?
An end-of-line resistor is used by alarm panels and other monitored inputs to supervise circuit state.
What is a tamper circuit?
A tamper circuit monitors whether a device, cover or enclosure has been opened or disturbed.
What is a monitored input?
A monitored input can detect more than just open or closed states, often using resistors or supervision methods.