Siemens 6DD1681-0AG2 SIMATIC TDC SB70 Interface Module with 8 Relay Digital Outputs Product Overview The Siemens 6DD1681-0AG2 is an SB70 interface module for SIMATIC TDC / FM458-1DP . It adapts 8 digital output signals to the plant signal level by means of relays with electrical isolation. Module: SB70 Interface Module System: SIMATIC TDC / FM458-1DP Outputs: 8 binary outputs (relay) (Allows multiple digital output signals to be connected through one compact interface module.