Abstract: Groups of stations operate in TDMA mode relative to associated frequency-separated transponder segments of a satellite repeater. Stations at radio signaling modes in all groups key to a common frame timing reference. The TDMA frame is partitioned repetitively into IN GROUP and CROSS GROUP intervals, each susceptible of containing multiple demand assignable burst time slots. Each node may transmit TDMA bursts (of time compressed and time multiplexed information signals) in assigned slots in either interval (or both). Such bursts are carried only on the transponder radio frequency associated with the respective group. Station receivers are adaptive to switch local oscillator frequencies in synchronism with transitions between IN GROUP and CROSS GROUP periods, and thereby adaptive to receive signals from stations in both groups.

Abstract: In a time division multiple access (TDMA) system, for "multi-path" data communication via satellite repeater, the form of transmitted data is varied adaptively to maintain error-free transmission under varying noise conditions. Adjustments are made on a path selective and channel selective basis to protect only the most vulnerable data in specific transmission paths experiencing noise deterioration. Accordingly any multi-channel burst may contain channels of data in both protected and unprotected forms. A predetermined portion of each channel containing data in unprotected format is used explicitly to designate the destination of the accompanying data and implicitly to distinguish the data format as unprotected. In protected format data including error protective coding is transmitted in two contiguous channels along with information in the first channel explicitly distinguishing the protected format.

Abstract: A method and apparatus are disclosed for acquiring transmit synchronization at a secondary station with the periodic frame reference bursts from a reference station in a TDMA network in an improved manner to enable the use of full power initial acquisition bursts while also reducing the bandwidth required to complete the initial acquisition operation. During the first phase, the apparatus at the secondary station bursts an initial acquisition burst during a relatively wide interval in the traffic portion of a TDMA frame and measures a propagation delay factor. The apparatus then adds the propagation delay factor to the receive frame timing synchronized with the reception of the frame reference bursts at the secondary station to obtain a more accurate adjusted transmit frame timing.

Abstract: A multiple data rate digital switch for a TDMA communications controller is disclosed which can service a plurality of input/output ports having many different data rates on a time divided basis, either between ports connected to the same controller or between ports connected to different, geographically remote controllers. A transmit burst buffer and a receive burst buffer are connected between the local ports and a TDMA communication link and an intranodal buffer is connected between local ports. All three buffers are accessed by a switch control memory which stores n.sub.i control words for each of the ports which are scanned m times per TDMA frame, there being a frame rate of f frames per second. Thus, the ports are selected and their data is buffered at a rate R.sub.i which is equal to the product of n.sub.i times m times f. In this manner, ports having a variety of data rates can be serviced on a time interleaved basis with maximum connectivity.

Abstract: The position of a channel of information transmitted from a particular port is varied in response to the changing priority of that port's messages as time passes. Variable priority assignments become necessary when low speed data has been deferred in its transmission until a time just prior to the production of a second unit of data. The effect of changing the priority of deferred data messages in a TDMA burst is to change the relative position of the associated channel within the TDMA burst by means of compiling the address of that message in a higher priority threaded list.

Abstract: The transmission and reception pattern generators are synchronized for all data ports operating at the same data rate throughout an entire TDMA system. This eliminates the necessity for bit stuffing to accommodate non-integral multiple data rate data ports and yet allows data activity compression operations to be carried out.

Abstract: To make the most efficient use of the TDMA frame for a satellite communications network, the assignment of each local station's TDMA burst duration is based on a statistical assessment of the demand by local voice and data ports. Occasionally the actual voice and data port demand at a local station exceeds that station's assigned burst duration so that some of the messages which are ready for transmission cannot be transmitted and may be frozen-out. To avoid or minimize the effects of message freeze-out, the various types of messages are categorized into a hierarchy of priorities for transmission.

Abstract: A roller cutter type earth boring drill having a ball bearing race filled with ball bearings through an external passage has the passage filled with a bearing retaining plug having a symmetrically cut end portion fitting the curvature of the bearing race.