A permanent-magnet-type magnetic field generator capable of generating a strong magnetic field not weaker than 3 T in a magnetic field generation space is provided. Within the sextant system of M\u2014Al\u2014Si\u2014O\u2014N\u2014C\u2014Ln and quintuplet system of M\u2014Si\u2014O\u2014N\u2014C\u2014Ln, the phosphors are composed of either one single crystalline phase or two crystalline phases with high chemical and thermal stability. An extendable leg rest assembly allows the user to kneel thereon to further relieve lower back stress during prolonged periods of seating and to better enable the seat occupant to make use of a laptop computer or other equipment positioned in front of the occupant. The wire-tapping device collates the received information about the routing protocol traffic.