As its name indicates, the 16/12 has sixteen input channels and twelve output channels, but that doesn't mean you'll find that many connectors. First of all, we should point out that these numbers represent total monophonic channels, because that's the way professionals count, even though two linked channels are most often used to make one stereo input. The first ten input channels are balanced line inputs on the back of the unit, using ¼" (6.35 mm) stereo jacks. Channels 11 and 12 are separate, since they have a real configurable, adjustable preamplifier. They're on the front panel and use combo XLR/¼" jack connectors - the two most common professional standards.
Switching from line level to mike level is done separately for each input, via a potentiometer that lets you adjust the gain to suit the equipment you have connected. Each channel also has an "Instrument" switch for changing a microphone input to high impedance (100 k?) in order to adapt to an instrument output without having to use a direct box. Naturally, these inputs have a 48 V phantom power supply, to allow the use of static microphones. Be careful not to press this button at the wrong time, especially since it's common to both inputs!
If you count up all the inputs, you get twelve, whereas Hercules claims there are sixteen. The four missing inputs are supplied by the two S/PDIF (coaxial and optical) connectors, which are naturally stereo inputs. So in practice, you indeed have twelve analog channels and four digital channels for recording, for a total of sixteen.
Hercules counts the outputs the same way, meaning that there are eight analog channels (also balanced, using stereo 1/4" jacks) and four S/PDIF outputs. This seems quite sufficient for most possible uses. The outputs are well designed, but you may have to beef up your cable collection to adapt your equipment to your new device. Naturally there's also a headphone jack on the front panel, with its own volume control.
Input levels are indicated by a series of diodes - green for normal level, orange for near saturation, and red for saturated. For the outputs, only the presence of a signal is indicated, but that does spare you having to look for which input isn't working when there's a problem.
In addition to all these audio inputs and outputs, there are two pairs of MIDI connectors (input and output), one on the front and one on the back. There are also two Word Clock BNC plugs, which can send and receive data to ensure proper synchronization of the various digital equipment being used. This is a real advantage for users who have studio equipment!
The number of inputs and the possibilities for connection in general will be one of the 16/12's main strong points, but certain users will probably wish ADAT connectors had also been included.