Abstract: This chip-to-test (1) has a passivation layer and an overlayer at test points (4). The system comprises a vacuum chamber (8), means (2) for mounting and connecting the chip-to-test (1), a pulsed light source means (9) operable to scan the chip-to-test (1) for inducing photoelectron (15) emission therefrom, means (14) for exercising the circuits of the chip-to-test (1), means (18) for detecting the photoelectrons (15), having a detection threshold and delivering a sequence of signals representative of voltages at the currently scanned test point (4') or points as a function of the scanned point or scanning time, means (23) for flooding the chip-to-test (1) with electrons of energy lower than the detection threshold, means (21) for analyzing said sequence of signlas and means (22) for deriving therefrom a capacitive voltage contrast. The material of the overlayer has a work function lower than the photon energy and can be BeO, MgO, CaO, TiO2, more preferably SrO, Cs2O, BaO or a mixture thereof.

Abstract: In a communication system providing multiple access to transmission facilities for a plurality of stations (17, 21), two separate networks (11, 13) are provided: One is a token ring (11) on which access tokens and data are transmitted, the other is a high-speed optical fiber transmission ring (13) on which only large-volume data blocks are transmitted between particular stations (21) which are attached to both rings, but no access information. A token manager (27) in the token ring (11) provides at regular intervals particular tokens that are only used by the particular stations (21) for obtaining access to the high-speed ring (13), but also provides other tokens for regulating access to the token ring (11) for other stations (17). Special access nodes (23) are provided which allow to connect the particular stations (21) to the high-speed ring (13) without extending its length.

Abstract: A communication system comprises several transmission bus segments (A . . . G) to which data stations (ST) are attached. Node units (1 . . . 7) are provided for interconnecting the bus segments which are selectively activated in a predetermined sequence for authorizing message transmission by attached data stations according to any given access protocol. Thus, only small groups of stations contend for access, but all messages are distributed over the whole network. Activation of a bus segment is effected by an authorization message from an assigned node unit. A token message is used to pass the status enabling a node to activate its assigned bus segment, sequentially through all nodes of the network. Each node unit comprises a control unit (17) for sending and receiving token messages and segment activation messages, and further comprises unidirectional amplifier means and switches (11) for establishing a connection between two associated bus segments selectively in either direction.

Abstract: In a network of communication rings (R1 . . . R7, BB) interconnected by bridges (B1 . . . B4), access to each ring is regulated by a circulating token which is normally issued at irregular intervals depending on occurrence and length of messages. To enable communication of messages which have to be transmitted synchronously, i.e., at regular intervals, each ring has a synchronous bandwidth manager SBM which periodically issues a token for only synchronous information. Each SBM is located in a bridge node (13, 15) but only one of them which is located in a particular bridge node (15) is the master SBM from which all other SBM's are synchronized, using a synchronous token and/or special synchronization circuitry in each bridge. This allows a common period in the whole network for handling synchronous information, even if all rings have different bit rates.

Abstract: In a communication network comprising block switching nodes interconnected by transmission links, a flow control mechanism is provided in each switching node for regulating the flow of addressed data blocks or messages. A hardware look-ahead mechanism effective within each node tests for each data block received from a link and buffered at an input port, whether it can be accepted at the appropriate output port of the same node for further transmission. A token mechanism effective over links permits maintenance at each output port of a node of an indication whether any data block can be accepted in the input port at the other end of the respective link. By the combined operation of look-ahead mechanisms and token mechanisms the flow of addressed messages in a direction where the transmission path is already filled up is prevented. This has a positive smoothing effect on overall traffic flow where short-time or local overloads occur.