Abstract: Silencing equipment is provided for an air-cooling assembly in a large off-road vehicle having wheels, traction motors for the wheels that operate in a motoring mode to propel the vehicle and a power generating dynamic braking mode, resistor grids for dissipating the dynamic braking power, and a blower for moving cooling air past the grids to cool them. The silencing equipment may include a resistor grid housing 24 and at least one upper inlet 22 for passing cooling air to the interior of the housing. The inlet includes noise-absorbing material. A conduit 28 is provided for directing cooling air from the upper inlet through a transition chamber to reach the blower and at least one resistor grid in the housing. The conduit is lined with noise-absorbing material. A removable cover 30 is provided for the conduit for accessing the air blower in the housing through the transition chamber, whereby servicing of the blower may be performed without removal of the entire upper inlet.

Abstract: 1. Means for searching across a frequency band and instantly stopping at any received frequency, comprising a detector, means for heterodyning said received frequency being connected to said detector, variable oscillator means, means for periodically varying said oscillator over a range of frequencies, means for injecting the frequencies of said oscillator in discrete steps into said heterodyning means, a pulse generator, a pulse-blocking bistable gate means coupling the output of said pulse generator to said oscillator means, pulse-shaping means associated with said detector to instantly form a pulse upon reception of said any received frequency, and means connecting the output of said pulse-shaping means to said gate means to open it in response to pulses from said pulse-shaping means, whereby the frequency variation of said oscillator means is discontinued and it provides a particular frequency in response to the output of said pulse-shaping means.