A device for monitoring power conditions in the power leads of a communication network or power distribution bus includes a microprocessor 54 which measures the voltage on the power leads and computers a filtered bus voltage, Vbus, and a time-averaged bus voltage, Vave. The apparatus includes a case with air passages, and a heat dissipation plate structure having a thermally conductive material within the case. The two-dimensional arithmetic unit performs two-dimensional operation. , at the first socket side shield members. Examples of the aromatic diisocyanate include toluene diisocyanate, phenylene diisocyanate, andor methylene di-p-phenylene diisocyanate.