Agilent Technologies 6621A Operating Manual page 53

The internal equivalent OV circuit is shown in Figure 4-9. Note the internal DC blocking capacitor, bleed resistor and noise
bypass capacitors.
Do not exceed 50 volts maximum between the + OV and the - OV terminals. The OV terminals are
rated at ±240 Vdc (including external OV voltage) from chassis ground or any other output terminals.
Figure 4-8. External Trigger Circuit
Figure 4-9. Equivalent Internal OV Trigger Circuit
Output Connections and Operating Information 53