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Special wiring rules apply to wet or corrosive locations, [13] and to locations which present an explosion hazard. [14] Wiring materials for use in the United States must generally be made and tested to product standards set by NEMA and Underwriters Laboratories (UL) and must bear approval marks such as those set by UL.
The stability of the voltage and frequency supplied to customers varies among countries and regions. "Power quality" is a term describing the degree of deviation from the nominal supply voltage and frequency. Short-term surges and drop-outs affect sensitive electronic equipment such as computers and flat-panel displays.
A quick light, abbreviated "Q", is a special case of a flashing light with a high frequency (more than 30 [3] or 50 [2] per minute). If the sequence of flashes is interrupted by regularly repeated eclipses of constant and long duration, the light is denoted "interrupted quick", abbreviated "I.Q".
for AC having a supply frequency of 50, 60 or 400Hz, though the use of other frequencies for special purposes is not excluded. This includes low-voltage installations, as found in most domestic and commercial properties, and extra-low-voltage systems, but excludes high voltage , as found in generation, transmission and distribution networks.
802.11 Beacon frame. A beacon frame is a type of management frame in IEEE 802.11 WLANs. It contains information about the network. Beacon frames are transmitted periodically; they serve to announce the presence of a wireless LAN and to provide a timing signal to synchronise communications with the devices using the network (the members of a service set).
In fixed wiring, the blue/brown scheme is only found in newer (post-2004) installations, and the old IEE red/black scheme is likely to be encountered in existing installations for many more decades. Earlier in the 20th century, green and blue were used as a neutral alongside black, which became the only neutral colour from 1943.
A Universal LNB has a switchable local oscillator frequency of 9.75/10.60 GHz to provide two modes of operation: low band reception (10.70–11.70 GHz) and high band reception (11.70–12.75 GHz). The local oscillator frequency is switched in response to a 22 kHz signal superimposed on the supply voltage from the connected receiver.