Abstract: The four signaling bits contained in the eight-bit SONET signaling bytes are read from the SONET signaling row and are converted to four parallel signaling bits for storage in a RAM in quasi-SONET format, with sets of four A, four B, four C and four D bits for four consecutive channels being stored for an even and an odd tributary in one RAM memory row. Storing sets of four of the same bit for four consecutive channels simplifies the RAM write operation. A read-modify-write system is used for updating the RAM storage, wherein a row of RAM is read, modified by eight new signaling bits from two consecutive SONET signaling bytes, and is rewritten into the RAM. New signaling bits are stored to accumulate eight new signaling bits for two tributaries prior to updating the RAM with the new bits for both tributaries. The 32 signaling bits output during a RAM read operation are selectively multiplexed to output only four bits associated with a particular channel.

Abstract: A method is shown, along with apparatus for accomplishing same, for minimizing power required to keep an enclosed electronic module from overheating in a high temperature environment, while still operating to maintain the module at greater than a given minimum temperature when the environmental temperatures are far below the sensed minimum temperature for the module. This is accomplished by placing a thin sheet of heating material between the module to be temperature maintained and a heat sink which is exposed to the environment exterior the enclosure. Energy applied to the sandwiched heater prevents transfer of heat from the electronic module to the environment in such a way as to drastically reduce the heat (power consuming) requirements as compared to prior art heater approaches.

Abstract: Two pulse-width modulated power supplies are synchronized to operate at 180.degree. of phase shift to reduce the peak amplitude of the instantaneous current drawn from the DC input bus. The circuit includes means for disabling the synchronization upon detection of an undervoltage fault condition on the output of either supply. This feature allows frequency programming techniques to be used to provide foldback current limiting for either supply without affecting the operation of the other supply.

Abstract: A self-locking system for use with circuit board holding frames comprises two side panels each having a specially configured slot for guiding a retainer bar, which extends between the two slots, between a locked and a loading position. Each slot has a shape similar to that of an upside down "L" and is positioned on each side panel at the top corner adjacent to the holding frame opening. In the locked position, the retainer bar, which is held in the guide slots by shoulder screws at each end, extends across the frame opening thereby blocking any outward board movement. In the loading position, the retainer bar rests out of the opening thus providing clearance for board removal or installation. A lip, which prevents the retainer bar from inadvertently toppling down into the locked position, is dimensioned so that the retainer bar may fall down into the locked position upon sufficient mechanical vibration if the system is mistakenly left unlocked.

Abstract: Overvoltage and component failure protection for redundant current-mode controlled power supplies operating in parallel takes a supply off line when the supply drives the output bus to an overvoltage condition, without removing properly functioning supplies from the bus. The supply is also taken off line when either the error amplifier or the PWM fails.

Abstract: An algorithm is presented along with circuitry for implementing same to accomplish the interface of a pair of synchronized data lines with a pair of non-synchronized data lines using data buffers where there can be as few as three cells of data buffers to accomplish reading data out and writing data in without interfering one with the other. This algorithm is accomplished by measuring the time skew between overhead bits of the two non-syncrhonized data streams and writing to the frame most recently read by the synchronized data stream based on an algorithm formulated in view of or based on a function of the time skew.

Abstract: A low inductance shielded cable connector to printed circuit interface with an isolated chassis ground can be obtained by a multilayer printed circuit board and plated-through holes. Two or more layers of the printed circuit board are used to provide a capacitive connection to chassis ground and other layers are used to provide connections for signal ground (cable ground) and signal connector leads. The direct contact of the shielded cable connector to a multiplicity of points on the exterior layer of the printed circuit board, wherein the contact points completely encircle the signal conductor, substantially eliminates both radiation of signal and pickup of signals by the signal conductor.