Janis Interphase 1A crossover/amplifier from mid 1990s, serial #2647.
Classic 18db high/low pass crossover at 100Hz with integral 80 watt mono amplifier.
Adjustable phase, bass level, and bypass switch.
Rarely offered for sale and somewhat collectible. Original price $825, sell for $165. Buyer to pay shipping. Read my feedback to be assured of a smooth deal.
Note: if you have to ask multiple questions about what this is or how it operates, it probably is not the unit for you. Please do your research before committing to buy.