A-151 : Very useful

This is an example of a module that does a specific thing very well.

You can use it to route four things to one destination, so you can have different vibrato rates for each step of a sequence, or you could route one thing to four destinations - take an LFO and modulate the cutoff frequency of a filter on step one, the resonance on step two, the amplitude on step three and the pitch on step four.

The output (or input) is freely selectable for two, three or four steps so interesting rhythmic variations can be achieved; the reset input returns to step one, so you can restart the cycle at the beginning of the bar; or indeed, anywhere you choose.

This switch is at the bottom of the unit and is freely accessible.

The build quality is great, it arrived well packaged and had two screws to mount it into the case.

No manual, but this is available online. If you want to send signals around your modular synth in a reasonably inexpensive way then this is a great starting point. It may not be as fully featured as other sequential switches but it doesn't take up too much space and is rock solid.