Toshiba HV6AS Manuel D'Instructions

All HV6AS fixed mounted circuit breakers are
furnished with an undervoltage trip device.  The
undervoltage trip device operates to trip the
circuit breaker OFF unless 120VAC control
power is present at the terminals of relay UV.  

When the circuit breakers are shipped, the
undervoltage trip device is defeated by a factory-
installed plug (Fig. 32).  If this plug is left in
place, the circuit breaker will operate normally
without power applied to relay UV.  Removing
this plug (Fig. 33) activates the undervoltage trip
function.