A "b" contact - is one that is closed when the breaker contacts are open and open when the breaker contacts are closed.

Accessory (device) - an electrical or mechanical device that performs a secondary or minor function apart from overcurrent protection.

Accessory high-fault protector - a self contained unit housing fuses or high-fault protectors. It is constructed for use with specific breakers and to be connected directly to the load terminals of the breaker.

Adjustable circuit breaker - a circuit breaker that can be set to trip at various values of current, or time, or both within a predetermined range.

AIR (ampere interrupting rating) - the highest current at rated voltage that an overcurrent protective device is intended to interrupt under specified test conditions (NEC).

AFCI (arc-fault current interrupter) - a circuit interrupter that detects a wide range of arc-fault conditions.

Alarm switch (bell alarm) - see overcurrent trip switch.

Ambient temperature rating - temperature at which the continuous current rating (handle rating) of a circuit breaker is based; the temperature of the air immediately surrounding the circuit breaker which can affect the thermal (overload) tripping characteristics of thermal-magnetic circuit breakers.

Auxiliary switch - a switch mechanically operated by the main device for signaling, interlocking, or other purposes.

Bell alarm - see overcurrent trip switch.

Branch circuit - the circuit conductor between the final overcurrent device protecting the circuit and the outlet(s).

Circuit breaker - a device designed to open and close a circuit by non automatic means and to open the circuit automatically on a predetermined overcurrent without injury to itself when properly applied within its ratings.

Coil clearing switch - a mechanically operated switch in series with the coil of a shunt trip device which breaks the coil current when the circuit breaker opens.

Continuous current rating (handle rating) - the designated rms alternating current in amperes which a device or assembly will carry continuously in free air without tripping or exceeding temperature limits.

Continuous load - a load where the maximum current on the circuit is expected to continue for more than 3 hours.

CSA - Canadian Standards Association.

Current path (of a circuit breaker) - the current-carrying conductors within a circuit breaker between, and including, line and load terminations.

Current-limiting circuit breaker - a breaker that does not employ a fusible element and that when operating within its current-limiting range, limits the let-through I*I*t to a value less than the I*I*t of a half cycle wave of the symmetrical prospective current.

Current-limiting range - the rms symmetrical prospective currents between the threshold current and the maximum interrupting rating current.

Current rating - see continuous current rating.

Electrical operator - a controlling device that is used to open, close, and reset a breaker.

Frequency - the number of cycles per second for an alternating current system.

Frequency rating - the range of frequencies within which a product can be applied.

Fused circuit breaker - a breaker that contains replaceable fuses or high-fault protectors provided to increase the fault current interrupting ability of the breaker.

Ground fault - an unintentional current path, through ground, back to the source.

Handle rating - continuous current rating.

High-fault protector - a unit containing a fusible element intended for mounting in a fused breaker or accessory protector.

High interrupting rating - an interrupting rating in rms symmetrical amperes at one or more of the values listed in Table 15.

Instantaneous pickup - the current level at which the circuit breaker will trip with no intentional time delay.

Integral ground-fault protection - equipment ground-fault protection on grounded neutral systems provided by components internal to the circuit breaker.

Interrupting rating - the highest current at rated voltage available at the incoming terminals of the circuit breaker. When the circuit breaker can be used at more than one voltage, the interrupting rating will be shown on the circuit breaker for each voltage level. The interrupting rating of a circuit breaker must be equal to or greater than the available short-circuit current at the point at which the circuit breaker is applied to the system.

Inverse time - a qualifying term indicating there is purposely introduced a delay in the tripping action of the circuit breaker, which delay decreases as the magnitude of the current increases.

Instantaneous-trip circuit breaker - a circuit breaker designed to trip only under short-circuit conditions.

I*I*t (amperes squared seconds) - Is an expression related to the energy available as a result of current flow, meaningful only for adiabatic conditions and as used in this Standard means the I*I*t between the initiation of the fault current and the clearing of the circuit.

Lock-off device - a device supplied as a kit for field installation on a breaker used in a motor circuit to permit the breaker to be padlocked in the OFF position when required by the Canadian Electrical Code, Part I.

Moulded case circuit breaker - a circuit breaker which is assembled as an integral unit in a supportive and enclosed housing of insulated material.

Molded case switch - a device designed to open and close a circuit by non-automatic means that is not intended to provide overcurrent protection.

Overcurrent - any current in excess of the rated continuous current pf equipment or the ampacity of a conductor.

Overvoltage trip device - a trip mechanism that causes a breaker to open automatically if the voltage across the terminals of the trip coil rises above a predetermined value.

Prospective current (available current) - the current that would flow during a short circuit if the breaker and the wires used for its connection were replaced by a solid conductor of negligible impedance.

RMS - root-mean-square.

RMS current sensing - a method of determining the true rms current of sinusoidal and non-sinusoidal waveforms.

SWD circuit breaker - a breaker rated at 15 or 20 A, 347 V or less, intended to switch fluorescent lighting loads on a regular basis.

Shunt-trip device - a trip mechanism energized by a source of voltage, that may be derived either from the main circuit or from an independent source.

Thermal Trip - a trip element consisting of a bimetal that bends because of the heat generated by current passing through it.
The bimetal's bending force and deflection trips the circuit breaker during overload conditions.

Threshold current - the rms symmetrical prospective current at the threshold of the current-limiting range, where the peak current let- through in each phase is less than the peak of that symmetrical prospective current and the I*I*t in each phase is less than the I*I*t of a half cycle wave of the symmetrical prospective currant.

Undervoltage-trip device - a trip mechanisms that causes a breaker to open automatically if the voltage across the terminals of the trip coil falls below a predetermined level.