Abstract: Apparatus for transmitting a data stream between cards connected by a midplane breaks the data stream into a plurality of channels. The apparatus comprises a serializer for each channel. Serialized data is transmitted across the midplane to a deserializer at the destination. Sequential cells are sent in different channels. Cell ordering is preserved by staggering the start of cell transmission in the channels. The invention permits data to be transmitted across a mid plane using a reduced number of data lines. The data stream on each card may be carried in a wide bus at a relatively low clock rate. Apparatus according to the invention may be used to transmit an OC-192 data stream across a pin-limited interface.

Abstract: Apparatus for transmitting a data stream between cards connected by a midplane breaks the data stream into a plurality of channels. The apparatus comprises a serializer for each channel. Serialized data is transmitted across the midplane to a deserializer at the destination. Sequential cells are sent in different channels. Cell ordering is preserved by staggering the start of cell transmission in the channels. The invention permits data to be transmitted across a mid plane using a reduced number of data lines. The data stream on each card may be carried in a wide bus at a relatively low clock rate. Apparatus according to the invention may be used to transmit an OC-192 data stream across a pin-limited interface.

Abstract: A head assembly for a vacuum actuated printed circuit board test fixture includes a top plate adapted for receiving a printed circuit board thereon, a probe plate having a plurality of spring-loaded contact probes thereon, and a support assembly for supporting the top plate in sealed relation above the probe plate. The support assembly includes a primary seal member having a channel formed therein and a resilient secondary seal member in the channel which cooperates with the primary seal member to provide a seal between the top plate and the probe plate around the entire perimeter of the top plate and to support the top plate so that it is movable toward the probe plate by resiliently compressing the secondary seal member.

Abstract: A test fixture for testing a printed circuit board assembly on a computerized test system includes a vacuum-actuated base which is receivable and securable in electrically connected relation on the test system and a vacuum-actuated test head which is releasably receivable on the base and adapted for receiving a printed circuit board assembly thereon to electrically interconnect the printed circuit board assembly to the test system through the base. The test head is readily interchangeable with other test heads to enable the fixture to be adapted for testing printed circuit board assemblies of different configurations on the test system without disconnecting the base from the test system.