A computer and switching mainframe connection system and flat cable connection elements therefor. The elements are a flat cable ''S'' circuit, (Fig. 1), and a bus circuit (Fig. 8). The ''S'' circuit has an elongated run (68) and a ''S'' portion (43). The bus circuit has ''U'' elements (61) and a linear portion (58) with the signal lines of the ''U'' elements (61) connected to the signal lines of the bus circuit (80). The mainframe is formed of an array of circuit boards (100) bearing a wafer (90) and header (99) for the wafer which in turn is connected to ports (101) to which tab connectors (57, 56, Fig. 3) of the bus circuit and ''S'' circuit are connected.