Abstract: A fiber optical circulator includes a first collimator and a second collimator sandwiching a circulator core therebetween. The first collimator and the second collimator respectively define Port 1 and Port 2 thereof, and the first collimator further defines Port 3 thereof. The circulator core includes a first crystal and a second crystal at two ends respectively confronting the first collimator and the second collimator aside. The circulator core further includes a first group of two half-wavelength waveplates and a first Faraday rotator, and second subassembly a second group of two half-wavelength waveplates and a second Faraday rotator. A third crystal is disposed between the first subassembly and the second subassembly wherein a backward light path from Port 2 to Port 3 passes the third crystal and is deflected by the third crystal toward the first collimator though total internal reflection.

Abstract: An electric heating unit for heating fluid, such as air in a hair drier, includes two ring-shaped electrodes and a plurality of spaced, plate-like ceramic heating elements having a positive temperature coefficient of resistance (PTC) aligned between the electrodes. The electrodes comprise an inner ring and an outer ring disposed in a nested, concentric, spaced relationship. The PTC ceramic plates are radially arranged in aligned spaced relationship with the opposite ends of each PTC ceramic plate mechanically and electrically connected respectively to the inner and outer rings. The inner and outer rings can be formed as arc-shaped segments separated by gaps prevent damage to the PTC ceramic plates by heat strain, and are provided with slits, grooves, etc., for firmly positioning the PTC ceramic plates.