The instrumentation transformers 6a to 6d and 7a to 7f for measuring the voltage of the main circuit are arranged within the container 15b located in the midst of the containers 15a to 15c. The echo canceller circuit includes a digital filter having adaptive tap coefficients to simulate an echo response occurring during a call. The cart base and the cart sidewall cooperating to form a tool storage compartment. 0 device to provide accurate and proper timing signals needed. Also included is a cavitation assembly at the outlet portion of the vortex generator which creates cavitation.