Partner modules are assigned to a plurality of primary modules in a communications system, each partner module being adapted to route signals from the primary module to which it is assigned to a spare module in case the primary module fails. The partner modules preferrably also serve as primary modules for receiving signals from their associated communication lines. As a result, redundancy for a failed primary module is provided by a signal routing architecture that is distributed throughout the communications system.

A micro code operated microsequencer that includes a monitor, a timer, a function controller and an address controller controls the functioning of a number of operational stations which exchange address and data signals with the microsequencer over a bus. The stations have designated tasks to perform and are selectable by the controller. When the station selected performs a task that requires a read from a RAM memory, the microsequencer selects a time-out duration during which the selected station is expected to complete its assigned task which is long enough to take into account the added time needed to perform the read from memory. If the station selected performs a write task, the microsequencer selects a shorter time duration during which the selected station is expected to complete this task since no memory read is needed. If any assigned task exceeds its appropriate time-out duration, an error condition will be sensed and the microsequencer will not receive an active Continue signal from the selected stations as long as their assigned tasks remain uncompleted.

In a system including a parent station and a plurality of child stations connected only to the parent station, which is unable to detect a response among the plurality of child stations, the parent station includes a transmission permission sequential allocation mechanism for giving transmission permission sequentially and a first timer for monitoring a first period which is a response detection time period. The child station includes a transmission permission detection mechanism for detecting that the identifier sent by the parent station is directed to the own station. Each of the child stations transmits data in a band period when the child station is permitted to communicate. When the parent station does not receive a response from the child station permitted to communicate within the first period, the parent station permits a next child station to communicate.

In a processing method for a distributed processing system have a plurality of processors connected through a network for transferring programs among the processors, each processor introduces a program which circulates in the network, assesses the state of the processor for storing the program in that processor, and judges on the basis of the assessment information whether the introduced program is to be executed in that processor.

A vehicle visor includes a visor body for attachment to a vehicle, a mirror and a light source mounted to the body, and a lens attached to the body for controlling the distribution of light from the light source. The lens includes a surface with microvariations formed therein to define a holographic optical element that directs the light into a predetermined pattern for illuminating the face of the user. The lens so formed eliminates undesirable uneven light distribution such as "spider webbing," light/dark patchiness and chromatic aberrations in and around the predetermined light pattern.