The original CZ-6 had a "pigtail" connection for the headphones, and maybe the coil cable, I'm not sure. They redid that to the modern 5-pin connection and a 1/4" jack for the headphones with the CZ-6A.
The 6A is an old, but still top-notch unit. Basically, it's just like the CZ-5 (which I use as my primary land detector), except it doesn't have an external speaker, and it "weather-resistant". Honestly, I wish they had never discontinued that one, as I will ocassionally hunt in a light rain, with my coat draped over my hipmounted CZ-5.
If you don't have a manual, go to Fisher's website, on the contact page, at http://www.fisherlab.com/contact_us_Form.cfm and see if they will send you a manual for it. Email them, and ask about the Adobe .pdf version, and they may have it back to you that day.
Learn how to properly ground-balance the unit, then, go to a site with easy digging and plentiful targets to learn the tones. Have fun.
HH from Allen in MI