You can connect it to a PA or mixing board via the stereo outputs and it can receive and send MIDI information. The Pads are velocity sensitive and the volume is being adjusted with the big knob on the right.
For a drum machine this unit is very easy and straight forward to program. People being used to having big screens and software drum machines might find it a bit cumbersome but really for it being a small portable unit things couldn't be any easier. If you have any questions I found the manual to be very helpful and always task oriented.
You can choose which sounds you want on the 12 trigger pads (there is a selection of more than 300 sounds) or you can just choose a preset drum set. You can either create patterns or then tie them together to a song. For each pattern there are two versions, two fills, intros and endings.
Still after all these years (I believe the unit was introduced now almost 20 years ago) the sounds are pretty good. Of course these days you have higher sampling rates and different velocity layers...
...but it just shows that it's not necessarily about bits and kHz or tons of layers. These sounds were captured and then processed very well and have a lot of punch while being very naturalistic. The Alesis reverb is what it is - so don't expect studio quality...on the other hand you can still find the DM5 Module in many studio racks (which has basically the same sounds)...
I think they did a good job back then and it speaks for itself when a unit like the SR-16 is still in demand today.
As I said I have been using this drum machine for over ten years now and it has never let me down. I dropped a flower pot on it and spilled several cups of coffee over it. Although the volume knob has taken its toll it still works fine and if it ever breaks I will definately buy a new one (they just put out an updated version...so it would probably be that).
If you check on ebay or the audiofanzine forums you will see that they quite cheap and you do get a very good instrument for your money.