which is the modulus of ketron? it's like the sd1?

which is the modulus of ketron? it's like the sd1?

I have been told the SD2 module. I have the SD2 but not the SD1 keyboard.

The XD3 is the module version of the SD1. Both shared many similar parts including the CPU boards - but they are not identical in that the SD1 had all options included as standard whilst the XD3 could be upgraded as required (pattern expansion, hard drive, vocalizer etc)