Acoustic microscopy acoustic microscope (CSAM), and C-mode scanning acoustic microscope (C-SAM). More recently acoustic microscopes based around picosecond ultrasonics systems have demonstrated acoustic imaging in cells using sub-optical wavelengths working with ultrasonic frequencies into the multi-GHz. Since the vast majority of acoustic microscopes in use today are C-SAM type instruments, this discussion will be limited to these instruments. Ultrasound is broadly defined as any sound having a frequency above 20 kHz, which is approximately the highest frequency that can be detected by the human ear. However, the acoustic microscopes emit ultrasound ranging from 5 MHz to beyond 400 MHz so that micrometre
Radio-controlled aircraft the 1983 FCC reform that introduced "narrowband" RC frequencies - at 40 kHz separation from 1983-1991, and finally at 20 kHz separation from 1991 onwards, to the present day with fifty frequencies on 72 MHz solely for flying models. The 75 MHz band became usable only for ground-based RC modeling (cars, boats, etc.) in the same timeframe, with the transition also occurring through to 1991, having 30 frequencies available at the same 20 kHz channel separation. Canadian modelers today flying on VHF-band RC gear use the same 72 and 75 MHz frequencies as American hobbyists do, for the same types