Yes, 10-4 all the time. iirc you would say like "unit 9 (or whatever unit you were) 10-7" if you were getting ready to be away from your radio. "Unit 9 10-8" when you just got back to the radio. This was before the hand held ones which came between the truck/tractor ones and cell phones. The truck/tractor ones had this big bracket on them so you could slide them in and out of whatever thing you were driving and every cowboy had their own.