Abstract: A tester for testing a circuit breaker includes a plurality of load elements each having a nominal fixed impedance and an electronic switch associated with each load element. The electronic switch, when turned on, electrically connects a corresponding load element in series with a circuit breaker load terminal and in parallel with none or with a number of other load elements. A controller turns on a number of the electronic switches selected to draw through a corresponding number of the load elements a test current selected as a function of a designated rated current for the circuit breaker and sufficient to trip open the same. A pulse width modulation circuit cooperates with the controller and with the electronic switches. The pulse width modulation circuit provides a constant magnitude of the test current to accommodate variations of the nominal fixed impedance or variations of the voltage of the load terminal.

Abstract: A digital multi-bandpass audio equalizer which is comprised of an analog multiplexer (10), a two-channel analog-to-digital converter (12), a digital-to-analog converter (22), and a digital signal processor which is programmed to provide an arrangement consisting of combined anti-alias filters/sample rate decimators (14), memory buffers at various sample rates (16), bandpass filters (18), and "virtual" potentiometers (20), structured in such a way that the digital filter elements which are operated at low frequencies are implemented at correspondingly low sample rates in order to minimize the amount of calculation involved, maximize computational efficiency and avoid the phenomenon of "rate inversion".