bottom of the keyboard, similar to that of a synthesizer keyboard action Throughout various incarnations, the key action has undergone several changes over time: Scaled Hammer Action (2003–2008 models) The original keyboard action, featuring a single or double sensors installed below the keybed. The weights are attached far back to the keys, giving it a slight resistance after the keys are released. It is also have a simulated weight in which lower notes are heavier than higher ones. Tri-Sensor Scaled Hammer Action (2009–2011 models) Tri-Sensor Scaled Hammer utilizes three individual sensors for each keys, two installed below the key's base, and one installed slightly further back near the hammers. The hammers are also modified to have less resistance and swings back faster upon release. The three sensors ensures precision response and improved touch sensitivity compared to its predecessor. Tri-Sensor Scaled Hammer Action II (2012–present models) A revamped incarnation of the previous action. The triple sensors are now installed right below the key's base, while the hammers remain unchanged. Furthermore, this action even features unique keys with simulated synthetic ebony and ivory texture and the sensor's response can be digitally adjusted to match the playing style realistically. The Scaled Hammer Action II has been described as being harder, more substantial and heavier compared to the previous versions. It is also widely criticized for its characteristic knocking noises when played at medium to high velocities, and considered as being heavier than a generic acoustic piano keys. Smart Scaled Hammer Action (2019–present models) Reduces size and weight without compromising playing feel. Included in PX-S1000 and PX-S3000 models. And the new 2021 models, PX-S1100 and PX-S3100. Smart Hybrid Hammer Action (2022–present models) Included in PX-S5000, PX-S6000 and PX-S7000. Models Models currently sold in black. Console models 2006 : PX-700 2007 : PX-720 2008 : PX-800 2009 : PX-730 2010 : PX-830 2012 : PX-750; PX-780 and PX-850 2013 : PX-A800 2015 : PX-760 and PX-860 2017 : PX-770 and PX-870 Standard models 2003 : PX-100 – the original Privia, with Dual-Element HL sound engine 2004 : PX-400R – first Privia with LCD display and auto-accompaniment capabilities 2005 : PX-110 – first model with ZPI Synthesis sound engine 2005 : PX-310 2005 : PX-500L 2006 : PX-300 2007 : PX-200 – first entry-level Privia model with AiF sound engine 2007 : PX-320 – first Privia model with AiF sound engine 2007 : PX-410R – minor