Bulgin PX0409/90

In electrical engineering, impedance is the opposition to alternating current presented by the combined effect of resistance and reactance in a circuit.

There are several different types of antennas in three broad categories: omni-directional, directional, and semi-directional.

The input impedance of an electrical network is the measure of the opposition to current (impedance), both static (resistance) and dynamic (reactance), into the load network that is external to the electrical source.

IP (or "Ingress Protection") ratings are defined in international standard EN 6529 (British BS EN 6529:1992, European IEC 659:1989). They are?used to define levels of sealing effectiveness of electrical enclosures against intrusion from foreign bodies?(tools, dirt etc) and moisture.