A reversible binary counter unit receives periodic clock pulses from associated advance train line apparatus, one pulse at the end or each cycle of operation of the ATL apparatus to vary train propulsion level in car by ear steps. The counter adds or subtracts each pulse in accord with the condition of an up/down direction signal representing the sign of the train speed error. The BCD output of the counter is converted into decimal form and applied to a 'select and/or' logic network which energizes the train line relay corresponding to the base propulsion level designated by the decimal count and all lower level train line relays. When the counter reaches either count limit, under a corresponding direction signal, further counting operation is inhibited through a logic network. The inhibit network also compares the existing propulsion level with a table of maximum propulsion levels selected for each range of allowed speeds and inhibits any increase beyond the preselected limit, thus enforcing the propulsion limits. The PTL apparatus also transmits a saturation signal to inhibit operation of the ATL apparatus when a propulsion level limit or maximum level is encoded.
PROPULSION TRAIN LINE ENCODER FOR A TRAIN SPEED REGULATION SYSTEM