UL 497B

Standard for Protectors for Data Communications and Fire-Alarm Circuits

1.1 These requirements cover protectors for data communications and fire-alarm circuits.

1.2 As covered by these requirements, data communications circuit protectors and fire-alarm circuit protectors consist of single- and multiple-pair air-gap arresters, gas-tube arresters, or solid-state arresters, with or without fuses or other voltage-limiting devices. Data communications circuit protectors and fire-alarm circuit protectors are intended to protect equipment, wiring, and personnel against the effects of excessive potentials and currents caused by lightning in communications alarm-initiating or alarm-indicating loop circuits.

1.3 This standard does not cover the following:

a)    Lightning protective devices for the protection of primary distribution wiring systems and equipment such as AC branch circuit protection.

b)    Antenna discharge units for radio- and television-receiving appliances.

c)    Lightning conductor and air terminals for connection of lightning rods for building protection.

d)    Protective devices to be used on telephone lines or telephone lines connecting to the telecommunication networks.

1.4 A product that contains features, characteristics, components, materials, or systems new or different from those in use when the standard was developed, and that involves a risk of fire, electric shock, or injury to persons shall be evaluated using the appropriate additional component and end-product requirements as determined necessary to maintain the level of safety for the user of the product as originally anticipated by the intent of this Standard.


  • Edition Number: 4
  • Edition Date: 06/14/2004
  • Price Code: A
  • Type: ulstd
  • ANSI Approved: 10/15/2008
  • DOD Approved: