Because we have moved slightly away from the pure VME style of bus towards a geographically organized bus, we can and must have two point to point signals running from each FEC to the Translator - the Select line and the Data Available line. These two lines act as a handshake system for data movement and the Select line eliminates a good deal of on board address decoding logic from the FEC. There are 16 Select and Data Available pairs for the FECs (0..15) and one more for the Trigger (although in its present implementation, the Trigger card does not have any source of data). The Select and Data Available lines for the Translator itself do not, of course, need to be on the backplane. These 18 pairs are directly connected to their respective registers. The Select line is implemented as GTL and the Data Available is implemented as ECL (because there are only two lines (DTACK and Data Available) running FEC to Translator and the large GTL transceiver chips handle 18 signals.