Yes, this information is found in the 6800 Service Guide, figure 6-21, sheet 1. See http://literature.cdn.keysight.com/litweb/pdf/5962-0859.pdf#page=109
The output barrier block on the rear panel of the 6800 (TB552) appears on the right side of the schematic. The output relays (K502 and 503) are normally open, until the output is turned on; either from the front panel, or from over the GPIB interface. The relays open when the output is turned off.
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