This standard sets terms@ test methods@ test circuits@ measurement procedures and preferred result values for series connected@ self-restoring current-limiter components used in low-voltage telecommunication circuit surge protection. It is only applicable for components in telecommunications circuits with sinusoidal ringing voltages up to 150 V rms at 15 Hz to 70 Hz and dc powering voltages up to 400 V. The selfrestoring current limiters covered by this standard have the following properties: ?? Excessive current causes a transition from a low-resistance state to a high-resistance state ?? Reverts to a low-resistance state when the excessive current ends ?? Directly operated by the current flow through the component ?? Solid-state (no moving parts) ?? Withstands specified levels of impulse ?? Withstands specified ac voltage levels when in the high-resistance state Examples of this type of current-limiter technology are positive temperature coefficient (PTC) stepfunction thermistors of ceramic or polymeric material and silicon semiconductor based electronic circuits. This standard does not cover self-restoring current-limiter components used in other applications@ such as heaters@ inrush-current limiters@ or sensing devices. Current interrupting type components@ which reduce the current to zero by a mechanical circuit break@ are not covered by this standard. In this standard@ a telecommunications circuit is a circuit that uses metallic conductors to handle the remote transmission of information@ such as data@ communications@ and signalling. Purpose The test criteria and terms of this standard provide a means of component comparison and a common engineering language for users and manufacturers of self-restoring current-limiter components intended for use in low-voltage telecommunication circuit surge protection. The test and measurement of low-voltage telecommunication (data@ communications@ and signalling) surge protectors is given in IEEE Std C62.36? [B6].1 This standard provides the corresponding component tests for the surge protector non-surge and active tests. 1 The numbers in brackets correspond to those of the bibliography in Annex A.