Tertiary Sources Tertiary sources are publications that summarize and digest the information in primary and secondary sources to provide background on a topic, idea, or event. Encyclopedias and biographical dictionaries are prime examples of tertiary sources.
From Wikipedia, the free encyclopedia. A value-added service (VAS) is a popular telecommunications industry term for non-core services, or in short, all services beyond standard voice calls and fax transmissions. However, it can be used in any service industry, for services available at little or no cost, to promote their primary business.
VAC = Voltage, Alternating Current You can find this voltage in wall-outlets, the well-known mains voltage with 50 or 60Hz frequency or a Voltage coming from a mains' transformer secondary winding (opposite of VDC which comes from batteries or rectified and filtered supplies) VA = Volt x Amper, power when the voltage and the current is not in phase.