At the heart of every recording system SHOULD be a patch bay, especially if you've got an assortment of sound sources and destinations.  In this case, it's respectively microphones and preamp inputs and preamp outputs and tape machine inputs.  As of December 2010 - details subject to change with notice -  the mic lines are half-normalled to the preamp inputs.  This means that re-routing a microphone requires that a dead patch be inserted directly  below it so it doesn't feed two preamps at once.   The preamp outputs are not normalled at all. 

Note the far left 'preamp output' is an oscillator, which is handiy for testing lines.  The only outboard not useable as a preamp are the two API equalizers.  "VF" stands for Vari-Fi or Variable Fidelity.  These preamps are based on Scott Hampton's JFET only these use negative feedback to adjust gain and have simple optical limiters.

Click on the bay to get a printable version...

In the future, the mics will be full normalled into the preamps so that re-routing automatically breaks the conection.  The preamp outputs will be half normalled to either the four-track or the multi-track tape machine.