Abstract: Apparatus suitable for detecting a fault in a processor comprises a monitor which receives input and output signals from the processor and generates a hash index key which is used to access entries in a hash table. The entries may include actions such as setting a timer so that the response of an output to a change of state of an input may be confirmed as valid within a specified time interval.

Abstract: The invention provides a variable focus lens formed from a ring with a front surface and a rear surface, a flexible membrane is attached to a radially inner part of the front surface, and a front cover is attached to a radially outer part of the front surface, a rear cover is provided on the rear surface of the ring, preferably integral with the ring, so that a variable volume cavity is defined between the flexible membrane, the ring and the rear cover, second flexible membrane can be provided between the ring and the rear cover, where the invention also provides a method of filling a variable focus lens, and an adjustment mechanism for varying the focus of the lens.

Abstract: The invention provides a variable focus lens formed from a ring with a front surface and a rear surface, a flexible membrane is attached to a radially inner part of the front surface, and a front cover is attached to a radially outer part of the front surface, a rear cover is provided on the rear surface of the ring, preferably integral with the ring, so that a variable volume cavity is defined between the flexible membrane, the ring and the rear cover, second flexible membrane can be provided between the ring and the rear cover, where the invention also provides a method of filling a variable focus lens, and an adjustment mechanism for varying the focus of the lens.