Organ brass pulse keyer

摘要

A brass pulse keyer for electronic instruments such as electronic organs wherein the tone during attack is both amplitude modulated and pulse width modulated. The keyer is adapted for large scale integration and comprises a timing capacitor, an electronic switch connected between a source of charging potential and a capacitor and having a control terminal which is connected to the tone input, and a second electronic switch connected in series with the charge voltage, the first switch, and the capacitor and having a control terminal connected to receive the keying envelope. A comparator compares the potential on the capacitor with a reference potential and disables a gating circuit when a compare condition is reached such that the duty cycle may be controlled. As the keying envelope continues towards its maximum, the duty cycle decreases so that a more brilliant tone is achieved. This signal is connected to the input of an analog keyer, which is also controlled by the keying envelope such that amplitude modulation of the tone may also be achieved.