1.1 This standard applies to resistors intended as laboratory a. c. resistors for use over a range of frequencies from d. c. up to a stated frequency which is not in excess of 100 kHz. Such resistors are hereinafter referred to as "a.c. resistors". 1.2 In addition to satisfying the requirements of I E C Publication 477, resistors satisfying the requirements of this standard are designed to have a small variation of resistance and a small phase displacement over the stated frequency range. 1.3 Because of the uncertainties in a. c. properties which can result from stray inductances, stray capacitances, eddy currents and dielectric absorption effects, the a. c. resistors to which this standard applies are classified according to their construction, as follows: 1.3.1 According to the number of main terminals, into one of the following types: a) Resistors having a pair of terminals at each point of connection. b) Resistors having a single terminal at each point of connection. 1.3.2 According to the method of protection against externally produced electric fields, into one of the following types: a) Resistors not having an electric screen*. b) Resistors having an electric screen which is permanently connected to one of the points of connection. c) Resistors having an electric screen which is not connected to the terminals of the resistor but which is provided with a separate terminal, sometimes called the "guard terminal". 1.4 In this standard, a. c. voltages and currents are assumed to have a substantially sinusoidal waveform. Note. – For general information about a.c. resistors, see Appendices B and C