Abstract: Apparatus for measuring the length of a transmission cable carrying primary and inverted multilevel transmission signals. A counter is arranged to count timing signals from the beginning of the measuring process while a filter extracts a high frequency signal component from the primary and inverted multilevel transmission signals. The extracted high frequency signal component is used to charge a capacitor. A comparator compares the level of charge of the capacitor to a reference level and issues a stop counting signal to the counter when charge of the capacitor equals the reference level. The count of the timing signals in the counter when counting halts is proportional to cable length.

Abstract: A combiner/memory system interconnects a plurality of computer systems using for example the new HIPPI standard link. The combiner system includes it's own internal storage for rapid shared access to all connected computer systems. The combiner/memory system includes a smart switch for reading header information, arbitrating messsages and connecting computers to each other or to the internal shared storage. The system also includes a mechanism for synchronization of cooperating processes.