A zoom lens includes, sequentially from an enlargement conjugate side to a reduction conjugate side: a 1st lens unit having negative refractive power not moved during zooming; plural lens units that are moved during zooming; and a final lens unit having positive refractive power that is not moved during zooming. The common apparatus performs communication with the server apparatus and acquires information on whether the power sources to all the client apparatuses on the network have been shut off, from the server. An ultrasonic vibration generator generates an ultrasonic vibration. In a testing method, a plurality of connection pads can be connected to a first potential and at least one of the connection pads can be connected to a second potential. The existing protocol stack software, upon completion of all connections initiated before the new protocol stack software was activated, is removed, services provided to the telephony resources being substantially uninterrupted by the modification.