[LAU] [Slightly OT] 312.5Hz

Hi Folks Slightly off-topic, but does anyone here know any audio significance of 312.5Hz? I have here a module from a piece of equipment dated back to 1968. It consists of a 4-pole, 50Hz motor, a printed disc, a lamp and a photocell. The printing on the disc (rotor) is a wiggly line of changing frequency which - according to the disc - represents a signal between 312.5Hz and 3kHz when spinning at 1500rpm. You light the lamp, spin the motor, then amplify the signal from the photocell. I've decided to use this as a tone source, replacing the filament lamp and photocell with an LED and LDR, or possibly a phototransistor. What I was wondering was whether end frequencies coincided with any musical notes. Cheers M -- Matthew Smith Smiffytech - Technology Consulting & Web Application Development Business: http://www.smiffytech.com/ Personal: http://www.smiffysplace.com/ LinkedIn: http://www.linkedin.com/in/smiffy