O
Obscuration
A reduction in the atmospheric transparency caused by smoke, usually expressed in a percent per foot.
Ohm’s Law
One of the most widely used principles of electricity. It expresses the relationship between voltage (E), current (I), and resistance (R), according to the following equations: E = IR; I = E/R; R = E/I.
ONVIF (Open Network Video Interface Forum)
A video industry standard for IP-based security products to ensure their interoperability.
Open Circuit
A condition where no electrical continuity exists in a circuit of conductor. In an open circuit protective zone, the detector contacts are open when the detector is in a quiescent state and closed in alarm.
Open Supervised Device Protocol (OSDP)
An access control communications standard developed by the Security Industry Association (SIA) to improve interoperability among access control and security products.
Openings and Closings
A prearranged schedule between the alarm subscriber and monitoring center for turning the system on and off. The monitoring center records this event and knows when a system has been left off inadvertently.
Opening Report
A report sent to the monitoring center at the time a system is disarmed showing who disarmed it, what area was entered, and the time and date the activity occurred. This information is often of interest to the customer for tracking user activity.
Operating Temperature
A temperature range that a device performs within its specified design tolerances.
Operating Voltage
The actual voltage applied to a device or circuit during its normal functioning.
Option
A user selectable function that can be accessed from the panel keypad User Menu.
Open Systems Interconnection (OSI)
A reference model put forward by the International Standards Organization (ISO) that provides a standard point of reference for networking protocols. It uses seven layers to break down the network process into independent processes.
Output
A Form C (SPDT) relay or switched ground (open collector) built onto a Command Processor panel or output expander module. Outputs can be controlled by schedules, panel programming, or manually from the keypad User Menu.
Output Action
A zone programming option that defines the following actions of an output assigned to a zone:
Steady: the output is turned on and remains on until the area is disarmed, an output cutoff time expires, or the output is reset from the keypad User Menu.
Pulse: the output alternates one second on, one second off.
Momentary: the output turns on only once for one second.
Follow: the output turns on and remains on while the zone is in an off, normal, or faulted condition.
Output Cutoff Time
A programming option that allows the user to specify a cutoff time for the panel outputs. If the output is turned off by the user, or by an event restoral, the cutoff time is reset and starts over at the next occurrence.
Output Schedules
Panel schedules that allow the user to set automatic on and off times for the outputs on DMP panels. Output schedules can be used to turn on exterior lights, HVAC systems, CCTV cameras, or any other contact activated devices. Outputs controlled by schedules can also be manually turned on or off by users with the proper authority level.
Outside Screw and Yoke (OS&Y)
A valve setup used in larger commercial sprinkler systems that contains back-to-back check and gate valves to allow water supply isolation from a building’s fire system.
Overlap
A problem that occurs when one device address is the same as any of the last three zones on another 714 or 715. The overlap feature cannot determine when two devices have the same address.
Oversampling
A technique used in communication where the condition of the line is sampled faster than the communicating device can transmit. This is typically used in Multiplexers.