(5) Application of 28 volt dc to close, allows momentary energizing of the coil . when the breaker closes, the coil deenergizes through the auxiliary contact and the breaker is held closed by the permanent magnet. Application of 28 volt dc to trip. Reverses the polarity of the coil and the contactor opens assisted by the spring. The coil deenergizes through the auxiliary contact.

28伏直流电关闭的应用，允许线圈瞬时接通。当跳开关闭合时，线圈通过辅助触点断电，跳开关通过永久磁铁被保持在闭合位。 28伏直流电松开的应用，将线圈极性反向，触点在弹簧的帮助下打开。线圈通过辅助触点断电。

(6) The 115 volt ac, 400HZ, 3-pahse power from an external source (ground power unit ) can also be supplied to the airplane for systems use. The external ac power system consists of an external power receptacle, bus protection panel, two external power contactors, relays, switches and indicating lights. The ac external power receptacle is located on the right side of the airplane, forward of the nose wheel well, the bus protection panel (BPP) is used for control and protection of the airplane circuits connected to external power. The two external power contactors connect 115 volt ac, 400Hertz, 3-phase power to the distribution system from external power source.

从外部电源的（地面电源） 400HZ，115伏三相交流电也能够提供到飞机上供系统使用。外部交流电源系统包括一个外部电源插座，汇流条防换板，两个外部电源接触器、继电器、开关及指示灯。外部交流电源插座位于飞机右侧、前轮舱前方。汇流条防护板用来保护与外部电源连接的飞机线路。两个接触器将外部来的 115伏， 400HZ的三相交流电源接到分配系统。

(7) The 115 volt ac system is supplied by two engine driven generators, APU driven generator or external power. The powr is connected to the generator main busses by engine generator breakers. APU breakers and external

power contactors. Power is also supplied to two transfer busses through transfer relays. External power can be supplied to the external ac bus and the ground service bus (this bus is used for servicing of the airplane). The ground service bus can also be supplied from generator bus NO.1.
115伏交流电源由两台发动机驱动的发电机、 APU发电机或地面电源提供。它被发动机跳开关、 APU跳开关或地面电源触点连接到发电机主汇流条上，它也可以通过转换继电器接到两个转换汇流条上。外部电源也能够供到外部交流汇流条及地面服务汇流条上。地面服务汇流条也能够从一号发电机汇流条供电。
(8) The 28 volt ac system is obtained through transrformers from main, transfer ,and ground service busses. The 28 volt dc power is supplied from the battery and transformer rectifiers to the battery bus and two dc busses. The power is connected to the busses by relays. The battery charger is supplied with power from the 115 volt ac system. The electronic system power is supplied from the 115 volt ac and 28 volt dc system. The standby ac and dc busses are powered normally from the generated ac and dc power. Alternately, the battery supplies power to the standby system. The standby power components are located in the electronics compartment, P6 panel and p5 panel .the purpose of the standby power distribution is to provide 115 volt ac and 28 volt dc power to essential system during absence of normal supply.