AV4 on E100

Just bought my panny E100 from Richer Sounds for a very reasonable £680-00. My first impressions are good, the hard drive footage is fantastic, even in sp mode it looks identical to the original. my question (probably first of many) is what does AV4 refer to, is it the sd card, or firewire input ?? or something else.

thanks

 

Its the s/vhs connection on the rear of the machine

Big Al

 

so it is, the manual certainly takes some getting through. thanks big al