I have several questions regarding drones and sensors. . I'd be grateful if you could alleviate my confusion

The 'sensor package' rules (pg325, SR4) have a number of sensor packages with various capacities, and on the same page there are various sensors that can be fitted to these packages. Now, I've looking in the 'SR4a changes' document and the FAQ. The FAQ seems to refer to me to a book I do not possess (which is a bit unfair, if you ask me). The SR4a document does answer some of my questions, but raises several more.

My questions are,

1) What sensors do drones have when they are purchased?

2) How can I change a drone's sensor package? Can I buy drones with specific sensors when I buy them?

3) If I purchase sensors with higher ratings than a drone's Sensor attribute, such as a Camera 6, does that mean the drone would apply a +6 modifier on Sensor tests when using the camera? Would Vision Enhancement and Audio Enhancement provide the same bonus to a drone's Sensor Test as they do to my Perception Test?

4) Specifically regarding the Smartgun System, the camera featured there can be enhanced (so it says in the description). However, it never says what its capacity is; can I just pick a Camera 6 and load it with all the goodies I want?

5) What is the point of having the Smartlink vision enhancement? I mean, the Image Link enhancement already displays visual data. The description of the enhancement explains that the Smartgun System interfaces with the Smartlink, but wouldn't it make more sense for the Smartgun to interface with the commlink? *can* it?t.

For drone sensors, use either the generic rating, which is listed in the gear section, or use the specific rating of the individual sensor if you have made that modification. Trying to combine them is a little tricky, though it can be done.

Smartgun systems are in parts, you need them all to have it work.