I would contend that a follow-spot needn't use IEEE floats to represent its DMX ID.
Maybe it's using some scripting language in which all numbers are floats?
That possibility had certainly occurred to me.
On the Chauvet Followspot 75, NAn is their shitty way of saying 'Manual'. I guess the seven segment display can't make an "M".
This seems most likely, since otherwise there's no reason to be using different "N" representations, but jwz's supposition is much more amusing.
A bit off-topic but if you're still searching for PTZ cameras for the lounge I've come to play around with some pretty nice ones (and very very cheap). Im using old Ploycoms MPTZ-5N and APTZ-2N. These have a S-VHS and composite output and are actually based on Sony's EVI-D100. They have a 12X optical zoom and full PTZ control from a serial port. They can be daisy-chained to manage up to 7 cameras with a single serial port connection and the control for it is readily available. I've found a few of the polycoms for around $10 to $30 on ebay. I've based the control of the cameras using
libvisca and wrote a little program around it to control it from a joystick. The nicest thing is that you can send both relative and absolute position commands and thus you don't need to rely on the camera's own memory for it. They are pretty sensitive in low light as they are based on the sony camcorder optical assembly.
I know you keep on searching for a web-controllable version (with its own web-server)... this one could be driven from a usb-to-serial on the main pc you use or maybe I can hack something up on a rPi with a rest/web interface to send the commands to it.
Anyhow... just wanted to share this.
I am not a number! I am a free spotlight!