Abstract: A Headend system including a encoder to encode input data yielding a plurality of data packets, each of the packets having a header and a payload, a post encoding processor to identify ones of the data packets having a payload with a suspected known plaintext, and modify at least some of the identified packets, and an encryption processor to encrypt at least some of the data packets yielding encrypted data packets. Related apparatus and methods are also described.

Abstract: A Headend system including a encoder to encode input data yielding a plurality of data packets, each of the packets having a header and a payload, a post encoding processor to identify ones of the data packets having a payload with a suspected known plaintext, and modify at least some of the identified packets, and an encryption processor to encrypt at least some of the data packets yielding encrypted data packets. Related apparatus and methods are also described.

Abstract: A plug current regulator for a dc electric traction motor propelled vehicle, implemented using a microcomputer for controlling a time-ratio switching regulator, provides a substantially smooth electrical braking function by applying relatively short time duration current pulses to build up braking current, followed by a relatively long time duration in which current pulses are inhibited. Current regulation is provided by comparing motor current to a desired braking current and generating an update signal when actual current drops below desired current. Filtering is minimized by sampling motor current at a time interval occurring relatively long after a current pulse is supplied to the motor.

Abstract: A current regulator for a dc electric traction motor propelled vehicle, implemented using a microcomputer, incorporates an accelerator response characteristics of an accelerator in an internal combustion engine powered vehicle. The regulator uses a current feedback loop to regulate motor torque to the value called for by the accelerator. However, of the magnitude of voltage as a percentage of available source voltage required to generate the desired current exceeds the percentage displacement of the accelerator, the applied voltage is limited to the percent accelerator displacement.