A PS3/2 board gives you the ability to upgrade a PS1 loco with the latest sounds, without the use of a battery. You can download either a PS2 or PS3 file. A standard PS2 board (now obsolete) You had only access to limited range PS2 sound files. Example would be a PS2 sound file is superior to it's predecessor PS1. A PS3 or 3/2 board board is superior to PS2 board. The Big Boy PS1 whistle now sounds 'flat' to our ears as compared to PS2. The PS3 version sounds 'hi-fi' with depth and more bass.