System key extension for ST 31, ST 40, 42 (IP) and 45 (IP) with 30 programmable function keys. Power supply: a separate plug-in power supply is required to operate up to two STE 40s; two plug-in power supplies (6100826) are required to operate three to four STE 40s on one ST 31, 40, 42 (IP) or 45 (IP)!