A Slew Limiter - also called a "Lag Processor" - is an example of a voltage processor. It produces no signal of its own, but affects those presented to its input. 

Slew acts upon rapid changes in a signal, slowing them by an amount determined by manual and/or CV controls. Portamento is a perfect example of slew applied to a control signal: the slew circuit smooths the transitions between the stepped CVs normally used to determine pitch, thus making one note 'glide' to the next rather than jumping abruptly as it would otherwise do. 

When applied to an audio signal, a slew limiter acts as a low-pass filter. On the RS-350 the maximum slew rate is about 100mS per volt, so a 1V signal can reach a frequency of just 5Hz before it is attenuated. (This is quite unlike the Slew Limiter in the RS-30 Frequency/Voltage Converter and Envelope Follower, which passes signals of up to 500Hz, or that in the RS-70 Pre-Amp, which allows signals of up to 5kHz to pass unimpeded.) 

Unlike the other slew limiters in the RS Integrator, the RS-350 is voltage controlled, allowing you to control the amount of slew (or 'glide') dynamically. This permits a number of interesting possibilities that are not available elsewhere. For example, applying the keyboard CV to the V-IN socket, and an inverted/offset keyboard CV to the CV-IN allows you to decrease the glide time as you play up the keyboard, and increase it as you play down the keyboard. This is a very 'natural' sounding effect, rarely found on electronic synthesisers. 

The RS-350 also offers an on/off CV that allows you to determine whether the original or the slewed signal is passed to the output. You can use this to jump between the target voltage and the intermediate, slewed voltage. This creates glissando type effects. You can, of course, use this together with the voltage controlled slew time to generate a wide range of unusual CV signals.