For warning time activation, it's a constant The HXP-3 crossing control unit uses advanced microprocessor technology to ensure consistent detection times with varying train speeds. The processor is available in three models: the HXP-3 for stand-alone operation in single- or double-track applications, the HXP-3R with built-in redundancy for single-track use and the HXP-3R2 with built-in redundancy for single- or double-track applications. | 
