Abstract: A textile dryer heat recovery system includes a textile dryer and a heat exchanger. A duct is provided for directing dryer exhaust gas to the heat exchanger for preheating dryer input air. A cleaning system within the heat exchanger removes dryer exhaust gas contaminants deposited in the heat exchanger.

Abstract: A circuit for detecting a difference in the relative magnitudes of two voltages includes a current sensing circuit connected between the first voltage and ground to thereby cause a first current to flow in the current sensing circuit, an amplifier connected between the second voltage and ground and connected to the current sensing circuit to thereby cause a second current to flow, the second current being equal to the first current when the first voltage is equal to the second voltage, and a variable impedance inverter connected to the first voltage and connected to the amplifier, the variable impedance being controlled by the first voltage, the output of the inverter thereby being related to the difference between the first voltage and the second voltage. The invention is particularly useful for controlling a battery backup power supply in a microprocessor having a volatile memory and for creating precision delay circuits.

Abstract: MOS Control circuitry for incorporation on a microcomputer IC chip for assuring adequate power to maintain the data in an associated static random access memory. A rechargeable battery provides standby power, and the voltage level of the battery is compared with the microcomputer V.sub.cc supply. Whenever V.sub.cc drops below a predetermined level, such as the standby battery voltage level, the circuitry disconnects the V.sub.cc from the memory input power and replaces it with standby battery power. When V.sub.cc is returned to the system, a gate applies a trickle charge to the battery.