Abstract: A trackerball arrangement includes a ball rotatably mounted with respect to a housing; a plurality of supports arranged to locate the ball in a predetermined operable position relative to the housing, at least one of the supports being mounted for movement away from the other supports; and being urged towards said other supports against a stop by the action of a resilient member acting upon it; whereby pressure which is applied via the ball to the supports causes movement of the supports when the applied pressure exceeds a threshold value which overcomes the force exerted by the resilient member. The movement allows lateral movement of the ball away from the other supports. The support is mounted on a spring loaded pivotable arm with an engagement part biased into contact with the surface of the ball and part of the pivotable arm is arranged to actuate an electrical switch mechanism.

Abstract: In a speed control arrangement for an induction motor or an a.c. permanent magnet motor in which any one of a number of power frequencies may be selected for application to the motor, there is provided circuitry to control the rate of change of frequency from one selected power frequency to another to control the acceleration or deceleration of the motor.

Abstract: Alkanediyl bridged benzimidazolo monomethine cyanine dyes are disclosed wherein at least one benzimidazolo nucleus is provided with an electron-withdrawing group. A disclosed preparation of the dyes includes producing an electron-withdrawing group substituted bis(2-nitrophenyl)-2-R.sup.1 -propanediamide, where R.sup.1 is hydrogen or alkyl; converting the nitro groups to primary amine substituents; removing the elements of water to effect ring closure; and thereafter providing the -CR.sup.1 - linked benzimidazole nuclei so formed with an N,N'-alkanediyl bridging group and quaternizing substituents. Dye synthesis is completed by reducing the -CR.sup.1 - linking group to the corresponding methine. The dyes are useful as sensitizers in silver halide emulsions and photographic elements.

Abstract: Alkanediyl bridged benzimidazolo monomethine cyanine dyes are disclosed wherein at least one benzimidazolo nucleus is provided with an electron-withdrawing group. A disclosed preparation of the dyes includes producing an electron-withdrawing group substituted bis(2-nitrophenyl)-2-R.sup.1 -propanediamide, where R.sup.1 is hydrogen or alkyl; converting the nitro groups to primary amine substituents; removing the elements of water to effect ring closure; and thereafter providing the --CR.sup.1 -- linked benzimidazole nuclei so formed with an N,N.sup.1 -alkanediyl bridging group and quaternizing substituents. Dye synthesis is completed by reducing the --CR.sup.1 -- linking group to the corresponding methine. The dyes are useful as sensitizers in silver halide emulsions and photographic elements.