Help with an amp?

I have an amp I removed from a car I bought secondhand some years ago I'm thinking of using and try as I might I just cannot find any information on it.
It's an ALTEC 4x100Watt unit, I understand it's pretty much old school stuff. Much like myself.
The basics I am pretty sure I have a handle on like the line inputs, the bandpass filters and the gain controls. The part that has me curious is on the output side where it has a plug labelled HI INPUTand underneath that it lies to me with the promise of a diagram on the bottom panel.
Would it be safe to assume this could be a suitable place to plug the output from an OEM head unit that has no low level RCA line outputs?
Cheers.

The hi output section has a plug that came with the amp, that plug has wires that you can connect to your stock wires off your head unit. I think that's how it is since I've never used the hi out option

Cheers for that!:thumbupw: