Btw note to build one of these at home an Arduino machine can work very well.  From wikipedia

Arduino is an open-source computer hardware and software company, project and user community that designs and manufactures kits for building digital devices and interactive objects that can sense and control the physical world.[1] Arduino boards may be purchased preassembled, or as do-it-yourself kits; at the same time, the hardware design information is available for those who would like to assemble an Arduino from scratch

For bit angle modultation it regulates the timing of the lighting of whether it is lit up or not.  Standard pwm is different in that it is just off or on.  Bit angle modulation could set on or off using bits in a pattern sequence of on on off on on etc and any type of combination depending on how long your sequence is.  And a note neon vs. LED in terms of energy usage is very different.  Neon runs hotter in a glass tube and LEDs can be up to 70% less energy usage.  Neon can look cool but in the digital age LEDs seem to take the cake with more capabilities.