Programmable equaliser with variable band pass characteristic - use either rotary selector or punched card optically scanned to give required band pass

摘要

A programmable equaliser for recording system applications has the band pass characteristic determined by either a rotary selector or by a data card with optical sensing. The band pass characteristic is determined by a chain of resistors (R1, R2,... Rn) each of which contribute 2-4 dB. The resistors are selected by outputs from OR gates (G1...Gn), with inputs from either a rotary switch (S1...Sn) or from photodiodes (PD1...PDn). The photodiodes are triggered by signals from a punched card (LK) with a common light source (LA). The columns of the card can be related to octaves and the rows to the number of attenuation steps per octave.