Based on Tangent's site, plus some advice from Morsel, I think.

Features:
1) 1/4" input from Amp output for flexible termination options (1/4" or 1/8" amp outputs)
2) Auxilliary 1/4" output to connect headphones or external resistive loads
3) tip probe sockets for multimeter
4) 33 ohm/330 ohm/ no load switchable option (On-None-On DPDT)
5) Switchable ground lift