Abstract: A wiper controller, responsive to any of a plurality of wash and wipe conditions, causes a short circuit protection circuit to inhibit control if the wiper motor becomes shorted. Hysteresis is employed for comparator operation of an intermittent wipe circuit that enables suitable short circuit protection.

Abstract: A knock detector for an internal combustion engine comprises a resonantly tuned knock sensor mounted on the engine, a variable gain amplifier for amplifying the signal from the knock sensor, knock and reference channels which are operatively coupled with the output of the variable gain amplifier to develop respective knock and reference channel signals, and a comparator for comparing the signal of one channel against the signal of the other channel. The gain of the variable gain amplifier, in general, is an inverse function of engine speed. The amplified signal from the variable gain amplifier is gated to a peak detector of the reference channel circuit during absence of any appreciable engine knock to develop a reference signal representing background noise. The knock channel detects peaks of the amplifier output signal, and the comparator compares the two peak detected signals to provide a knock signal when a predetermined relationship between the two is attained.