Communication circuits protectors
These devices are intended for use with telephone, telegraph, fire alarm and other similar signaling or communication circuits. They are designed to protect against high voltage and current conditions that may exist on the communication loop circuit.
Primary protectors for communication circuits (QVGV)
UL 497, the Standard for Safety of Protectors for Paired-Conductor Communications Circuits is used to evaluate protectors for use in exposed communication circuits as defined in Article 800 of the National Electrical Code®. This category includes both fuse and fuseless type protectors. These devices may also be used to protect against electrical transients from electromagnetic disturbances produced by lightning.
Secondary protectors for communication circuits (QVRG)
UL 497A, the Standard for Safety of Secondary Protectors for Communications Circuits covers protectors for use in communication circuits as defined in Article 800 of the National Electrical Code®. They are intended to limit current on communications circuits and may also suppress abnormal voltages that bypass the primary protector. They have been evaluated for use only on the equipment side of a primary protector.
These protectors may be stand-alone devices or may be incorporated into listed equipment with telephone interfaces to protect against over-voltage and over-current conditions that may occur.
Secondary protectors for communications circuits used with specified voltage suppression -- component (QVRP2)
Subject 497D, UL497A, the Standard for Safety of Component Secondary Protectors for Communications Circuits Used with Specified Voltage Suppression is intended for protectors used in signaling and communications circuits that are protected by a voltage-suppression device that has a suppression voltage less than the rated impulse voltage of the component. Special considerations need to be given to the tolerances and protection of the required voltage-suppression device.
Isolated loop circuit protectors (QVGQ)
UL 497B, the Standard for Safety of Protectors for Data Communications and Fire-Alarm Circuits is intended for protectors used on Class 2 or Class 3 remote control signaling and power limited circuits. These devices may be used to protect against electrical transients from electromagnetic disturbance produced by lightning on non-exposed wiring systems.
Protectors for coaxial communication circuits (QVKC)
UL 497C, the Standard for Safety of Protectors for Coaxial Communications Circuits is used to evaluate protectors for coaxial circuits as defined in Article 830 of the National Electrical Code®. This category includes both fuse and fuseless type protectors. These devices may also be used to protect against electrical transients from electromagnetic disturbance produced by lightning.
Coaxial fault protectors for network-power broadband communications systems (DUAA)
Subject 2389, the Outline of Investigation for Coaxial Fault Protectors for Network-Powered Broadband Communications Systems, is used to evaluate protectors that monitor the buried coaxial feeder cable for open conditions in the center conductor and for shorts or leakage current to ground from the center conductor. These devices are installed in accordance with the requirements of Article 830 (low power only) in the National Electrical Code®.
Protectors for antenna lead-in conductors (QVLA)
Subject 497E, the Outline of Investigation for Protectors for Antenna Lead-In Conductors, covers protectors used to limit surges on the antenna lead-in cable that connects the antenna to the receiver/transmitter electronics and are connected between the coaxial center conductor and the grounded shield (coaxial cable) or between the individual leads and ground including twisted pair, twin-lead, etc. Typical applications include antenna installations for radio and television receiving equipment, amateur radio transmitting and receiving equipment, cellular telephone towers and WiMax or WiFi wireless networks.
