Abstract: A technique for simultaneously transmitting wide and narrow optical beacon signals includes generating a laser beam and splitting the laser beam into a first signal on a first path and a second signal on a second path via a wavelength-dependent beamsplitter. A wide beacon signal having a first beam divergence is generated from the first signal, and a narrow beacon signal having a second, lesser beam divergence is generated from the second signal. The wavelength of the laser beam determines an allocation of the laser energy between the wide and narrow beacon signals based on transmittance/reflectance characteristic of the beamsplitter at that wavelength. The wide and narrow beacon signals are simultaneously transmitted in a overlaid manner into free space to support acquisition and tracking in a free-space optical communication system. The beamsplitter can simultaneously transmit or reflect substantially all of a data signal at a different wavelength.

Abstract: A technique for simultaneously transmitting wide and narrow optical beacon signals includes generating a laser beam and splitting the laser beam into a first signal on a first path and a second signal on a second path via a wavelength-dependent beamsplitter. A wide beacon signal having a first beam divergence is generated from the first signal, and a narrow beacon signal having a second, lesser beam divergence is generated from the second signal. The wavelength of the laser beam determines an allocation of the laser energy between the wide and narrow beacon signals based on transmittance/reflectance characteristic of the beamsplitter at that wavelength. The wide and narrow beacon signals are simultaneously transmitted in a overlaid manner into free space to support acquisition and tracking in a free-space optical communication system. The beamsplitter can simultaneously transmit or reflect substantially all of a data signal at a different wavelength.

Abstract: A detector includes a plurality of detector elements in a linear array. A bias source is connected to the input terminal of each detector element. The bias source includes a first bias connected to the input terminals of a first set of detector elements including alternating detector elements and is also connected through an associated measurement device to the output terminals of a second set of detector elements including the remaining detector elements. The bias source also includes a second bias, different from the first bias, and connected through an associated measurement device to the output terminals of the first set of detector elements. The second bias is also connected to the input terminals of the second set of detector elements.

Abstract: In an electrical propulsion system on board a moving traction vehicle (such as a rapid transit rail car) having current collectors in contact with an energized third rail, controllable switch means is used to connect the system to the current collectors. From time to time the current collectors traverse gaps between adjacent sections of the third rail, in which event regenerative braking operation of the system will be prevented unless the next third rail section is energized by a wayside source of voltage. The switch means comprises the parallel combination of a diode that conducts current when the system is operating in a motoring mode and a reversely-poled thyristor that conducts regenerative braking current once a firing signal is applied thereto.