P-120-U combines both manual and automatic control.

In "AUTO" mode the unit works like the P-120-A and offers constant speed operation. In "MANU" mode the operating procedure is as described for the P-120-M unit. Control units with serial numbers 97... and beyond have an additional yellow warning light, which indicates low voltage or an internal microprocessor error.

In case of a problem in "AUTO" mode, the circuit breaker must be pulled immediately. Afterwards the control unit can be switched into "MANU" mode and after having pushed the circuit breaker back in, the pitch can be adjusted manually with the center return toggle switch.

The brush block housing is made from a special plastic material and contains two carbon brushes and a RPM pickup. The wiring harness consists of 7 wires. Wire no. 1 and 2 connect to the electric motor, wire no. 4 and 5 connect to to the RPM pickup, the remaining three wires connect to the power supply (+, -) and to ground.

Counterweights can be installed at the blade ferrules for reducing the pitch change forces.

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