I have a handful of JJC sound modules lurking around my workshop.
This is, in my opinion an early Mk I JJC master sound module with selectable onboard sounds and an external input.
The push button is for selecting which onboard sound is required. Sounds were selected by pressing the button withing 5 secs from power on, then it will play each sound in order and you select which you want by pressing the button again. The status light flashes to acknowledge your selection.
The status light should flash once per second when ready for use.
Power on sequence will take 5 seconds whilst it waits to see if you want the setup mode.
The two blue 'pots' are Sound Pitch Control and Volume Control.
The small jack plug connects to further JJC sound modules. The MkI master units have the jack plug and the JJC slave modules have a socket. Later MkII masters used a socket.
As stated by Bluebird the units had a 15Watt amplifier and the voltage input could range from 6 to 18 volts.
I do not remember what an M101 contained, but I've an M102 which has 'Small Ships Horns' of which there were 3 to select from.
When used with higher voltages and long durations (constant engine sounds) they were inclined to overheat and cut out.
Later model MkII master units included a large heatsink to help but I've had to modify mine to include an onboard cooling fan blowing over the heatsink. It now 'sings' on a 4S lipo.
I still have some original instructions, if you are interested.