Abstract: A controller for controlling supply of electrical current to the coils or coil groups of an electromagnetic retarder for applying drag torque to a turning shaft or drive line. The controller includes an input signal receiving element for receiving input signals from at least one input device, a control unit responsive to the input signal for modulating electrical current supply from at least one current source to the retarder coils so that current is distributed to each of the coils or coil groups substantially equally.

Abstract: A magnetic tape cassette hub with an improved hub body member and tape retention means having a very low coefficient of friction is described for preventing separation therefrom of a tape also having a very low coefficient of friction. The hub described comprises a body member in which there is provided a cavity for receiving a latching member. The latching member is pivotably coupled, by means forming an integral hinging means, to the body member at one end of the cavity. On opposite sides of the hinging means, extending from the latching member and the adjoined side wall of the cavity, there is provided a pair of protruding members which overlap and are drawn together by the hinging means as the latching member is pivoted into and locked in the cavity. The tension forces thus produced in the latching member by the hinging means is found to provide a tape retention force which exceeds the yield strength of the tape even when the hub material is an acetal resin and the tape material is a polyester.

Abstract: A magnetic tape cassette is described in which there is provided a cavity in a rear wall of the cassette body for receiving a cavity sensing mechanism mounted internally in a cassette recording apparatus. The mechanism serves to enable and inhibit recording circuits in the apparatus as a function of its access to the cavity. A sliding door having at least two positions is provided to selectively open and close the cavity to the sensing mechanism to thereby provide control over the recording functions of the apparatus.