The present invention provides a battery chargingdischarging method for effectively using the battery energy of a power supply apparatus with a plurality of chargeable batteries. The detecting device has at least two series-connected optoelectronic transducers in the form of photodiodes. The control device is configured to determine, from the first and second signals, a reference signal indicative or a reference value of the frequency. The device of articulated arms is locked in the operating position when the upper arms are in an over-centering position once the lateral members have been coupled to fixing members. By locating an address latch circuit at an equal distance from each pad train, characteristics of the setup time and hold time can be improved. The protective cap can thus be used to protect the center conductor pin during shipping and then be used to cap the bore of the port terminator upon installation of the terminator in a multiport tap.