In a synthesis context, the lag processor is a circuit that goes by many names: slew limiter, portamento and glide. Freed from the constraints of the stereotypical usage, the lag processor can be so much more: an envelope generator, a simple filter, or an low frequency oscillator. Bissell Function Block circuit centers around a single quad op amp, the LM324N workhorse. This circuit contains four identical amplifiers, the slew limiter, a voltage follower (or buffer), a comparator, and a flip flop. A couple of NOT gates are built with transistors. The slew limiter is built around an RC (Resistor-Capacitor) network, with a buffered output. The RC network creates an adjustable lag time, and the buffer ensures that the voltage at the output matches the one at the input. A NOT gate only deals with logic signals—high and low states (on and off)—and will invert one value for the other.