The PedalBox is a very simple peripheral device that connects to a serial port and provides (via host software) a number of system-/program-control possibilites.
Because of its' simple hardware, it automagically works with both RS232 (12V) and TTL-level (5V) serial ports - without having to set any jumpers or switches, and without having to change any software settings.
It also will work at any baud-rate supported by the host system, and is self-identifing via the provided reference software (below).
For the curious, or those wanting to build their own PedalBox (it is relatively easy!), the original development project is documented at https://sparc90s.wordpress.com/2013/01/01/retrochallenge-2013ww/.
The event-stream reported by the monitor program is "plain text", so can even be interpreted (and acted upon) by a shell-script! See the protocol manual-page for details.
There are also online manual-pages available for the host-resident device-monitor and the Solaris program that uses the reported device-events to control the system speaker volume.
This is an SVR4-format package that can be installed via "pkgadd". It is a fully-relocatble package (can be installed in a base directory of *your* choosing, via the standard pkgadd techniques). This package includes manual-pages in standard SVR4 UNIX format.