The ADR Compex began life as a diode bridge limiter followed by a FET based design that was modified over the years to what we know today as the F760X-RS. ADR had different units that were combined to make the F760X-RS: F700 was the compressor, F600 was their broadcast limiter, the "X" indicated it had the Expander/Gate and "RS" indicated "Rackmount Stereo". So, adding these parts up gave them the F760X-RS. ADR supplied their "Compex" PCB's to other manufacturers such as Helios and Calrec to build into their custom consoles.
Circa 2005, Q2 Audio contacted ADR about putting together a re-issue and after a few re-designs that were tossed we arrived at the current Q2 Audio version. The original circuitry was kept intact other than adding better voltage regulation in a few spots as well as increasing local DC power decoupling to get better separation. The F760X-RS and F765 are being built by Q2 Audio in Royal Oak, MI.