R-410A than other refrigerants. R-410A systems thus require service personnel to use different tools, equipment, safety standards, and techniques. Equipment manufacturers are aware of these changes and require the certification of professionals installing R-410A systems. In addition, the AC&R Safety Coalition has been created to help educate professionals about R-410A systems. In accordance with terms and agreement reached in the Montreal Protocol (The Montreal Protocol on Substances that Deplete the Ozone Layer) the United States Environmental Protection Agency has mandated that production or import of R-22 along with other hydrochlorofluorocarbons (HCFCs) be phased out in the United States. In the EU
QSK operation (full break-in) QSK operation must ensure that their radio equipment includes the hardware capability for radio frequency antenna switching that operates rapidly enough to allow listening between signals at the appropriate Morse code sending speeds with appropriate lifetimes and reliability. QSK operation (full break-in) "Turning over" a communications channel is the change in communications protocol transmission status that occurs when a transmitting station releases transmitting control of a communications channel thus turning it over to allow another station to transmit. QSK or full break-in operation is one of several techniques and protocols for turning over control of a Morse code radiotelegraph communications