IEC 60153-4:2017 specifies straight hollow metallic tubing of circular waveguides for use as waveguides in electronic equipment.The aim of this recommendation is to specify for hollow metallic waveguides:a) the details necessary to ensure compatibility and, as far as essential, interchangeability;b) test methods;c) uniform requirements for the electrical and mechanical properties.This edition includes the following significant technical changes with respect to the previous edition:a) expand and revise the operation frequency range for waveguides;b) revise the allowance of aperture dimensions;c) revise the test method for aperture dimensions;d) revise the equation of attenuation.