So...what is an "internal accessory port" on the P3015N?

[Overkill]

I see what an EIO port is, but what is the internal accessory port and how is it useful for the consumer? What can be put in the port?

[Big Al]

If it looks like a socket for a Jet Direct NIC then you can put a NIC in here if your built in NIC port fails. You may also be able to put a hard drive in there, but I do not know why you would want a hard drive in there except to store fixed format jobs that need to be printed from time to time, such as forms, etc. I have never seen a hard drive in a printer but some folks do use them.

Al