TU551-CS31 is the screw-terminal version of ABB order code 1SAP210600R0001. It is designed as the field-wiring base for S500 CS31 communication interface modules that use 24 V DC inputs, outputs or interface signals.

The plug-in electronics can be released from the terminal unit while the bus and field conductors remain connected. This separates service of the active module from the fixed cabinet wiring.

• Dual B1 and B2 connection points simplify continuation of the CS31 bus through the station.
• Dedicated R1 and R2 positions support the specified end-of-line termination arrangement.
• UP and ZP provide the defined process-voltage connection for the inserted communication interface module.
• The female I/O-bus connector permits compatible terminal units to be connected downstream.
• Screw-clamp conductors support maintenance conventions where torque-controlled terminations are preferred.

• Distributed ABB CS31 stations using compatible S500 interface modules.
• Control-panel upgrades where screw-terminal field wiring must be retained.
• Maintenance replacement of a terminal base with documented B1/B2 bus polarity and functional-earth routing.
• 24 V DC remote-I/O assemblies requiring fixed wiring and removable module electronics.

• ABB lists 1SAP210600R0001 as an Active article.
• TU551-CS31 and TU552-CS31 are electrically related but use different field-terminal technologies.
• The selected host module must belong to the supported 24 V DC CS31 interface class.
• Before replacement, label bus polarity, termination links, process supply and every field conductor.