DATA COMMUNICATION LINK (DCL) also known as SIGNALLING LINE CIRCUIT (SLC):
The means employed by an ADDRESSABLE type control panel to communicate with compatible devices in the field. These may include INPUT DEVICES, OUTPUT DEVICES, ANNUNCIATORS, and remote TRANSPONDERS.
DELAY ZONE:
A circuit triggered by an INPUT DEVICE that allows the building occupants a set period of time in which to DISARM the ALARM SYSTEM. The time period is adjustable through system PROGRAMMING and usually takes into account how far the KEYPAD is from the main entry door. It is desirable to have the ENTRY DELAY set as low as possible.
DE-RATING FACTOR:
A term that usually refers to a multiplier used in the calculation of a BATTERY's standby capacity and which actually serves to determine the correct size of BATTERY to use in a fire alarm system or other critical applications. Building Code will specify the amount of alarm time required based on the type of occupancy. The number takes several factors into account which may affect the battery's capability to produce the required power over it's service life. These include age, cell degradation, charger condition, environmental factors, purity of the internal components, construction, etc. The most commonly used DE-RATING FACTOR is 1.3 (some would argue 1.2 or 1.25). A sample calculation (*based on a 30 minute alarm time requirement) is:
DIGITAL COMMUNICATOR:
This is an OUTPUT DEVICE utilized by the ALARM SYSTEM to communicate an emergency signal to a CENTRAL STATION or a pocket pager. It uses the premises normal telephone line to transmit the signal and is the most cost effective means of doing so. Some DIGITAL COMMUNICATORS employ TLM (TELEPHONE LINE MONITORING) to supervise for the sudden absence of the subscribers phone line which results in the activation of additional OUTPUT DEVICES to warn the building occupants or the CENTRAL STATION. You can read more about communicators in our TIPS section.
DIRECT LINE:
Also known as Dedicated Line and Direct Wire. This is a specially installed telephone line that links the premises ALARM SYSTEM directly to a CENTRAL MONITORING FACILITY or CENTRAL STATION. The line is supervised to prevent tampering. Any interruption is immediately signaled to the CENTRAL STATION and appropriate action is taken depending on the level of response required. In addition to certain types of FIRE ALARM SYSTEMS, banks, financial institutions, ATM machines, some jewelery and gun shops require this level of security. You can read more about communicators in our TIPS section.
DISARM: The act of turning off or deactivating a BURGLAR ALARM or SECURITY SYSTEM.
DOWNLOAD or DOWNLOADING:
Most modern alarm panels (both burglary and fire) are equipped with the ability to be programmed by a remote computer (or local laptop). The applicable software to perform this function is furnished by the system's manufacturer. This allows the MANUFACTURER TRAINED TECHNICIAN (or service company) to make changes to the panel's software and firmware which ultimately affects the operation of the system. It also helps to speed the set-up of the system and often incorporates "error checking". In the case of a fire alarm system, changes to programming (or the updating of firmware) will usually trigger the requirement for a VERIFICATION INSPECTION.
DUALTEC:
Refers to a number of INPUT DEVICES that employ two separate methods of detecting an alarm or fault condition (short for DUAL TECHNOLOGY) and thereby eliminating or severely reducing the chances of a FALSE ALARM in environments where single technology sensors may not be appropriate for use. DUAL TECHNOLOGY fire sensors typically incorporate both a smoke and heat detection components, activation of either of which will result in an ALARM condition.
DVACS:
Short for DIGITAL VOICE ACCESS CONTROL SYSTEMS. A means by which a number of ALARM SYSTEMS can communicate with a CENTRAL STATION over a network type of connection. Similar to DIRECT WIRE. It utilizes transponders connected to the CONTROL PANEL that are continuously interrogated by special receivers in the CENTRAL STATION. Many such receivers can also perform "on premises" functions like arming, disarming, zone bypassing, etc. You can read more about communicators in our TIPS section.