ABB TB807 3BSE008538R1 S800 I/O Modulebus Terminator

The ABB TB807 3BSE008538R1, also cataloged as the TB807 Modulebus Terminator, operates as a dedicated hardware component for passive line termination within ABB S800 I/O and System 800xA distributed control system platforms. Installed at the physical end of a optical or electrical Modulebus segment, it absorbs high-frequency signal reflections, maintains bus characteristic impedance, and prevents data bit corruption across the backplane communication network.

Hardware Specifications

Backplane Bus Communication Velocity and Signal Integrity

The TB807 terminator enforces physical bus matching across the S800 I/O cluster, stabilizing the high-speed differential signal lines against impedance mismatches. By eliminating voltage standing waves and signal overshoot at the backplane bus boundaries, the unit preserves backplane bus communication velocity and ensures error-free frame transmission between the field communication interface (FCI) and downstream I/O modules. The passive circuit design operates without active power draw, maintaining constant line impedance under varying operational thermal loads.

Frequently Asked Questions

Q: Does the TB807 terminator consume power from the Modulebus backplane? A: No. The TB807 is a fully passive impedance-matching device and draws zero current from the Modulebus 5 VDC or 24 VDC backplane power rails.

Q: Where must the TB807 terminator be installed within an S800 I/O cluster? A: The TB807 must be physically seated into the open Modulebus communication port on the final I/O terminal base or baseplate at the physical end of the Modulebus segment to prevent open-ended cable reflections.

Field Installation Guidelines

Verify that system power is deactivated before inserting or removing termination components from the backplane line. Align the TB807 terminator pins with the designated Modulebus expansion port on the last S800 I/O baseplate, pressing firmly until the connector fully seats into the housing.

Ensure no open or un-terminated Modulebus ports remain exposed at the end of the rack assembly. Maintain clean panel environments free of conductive dust and metallic debris, as contamination on the passive connector pins can shift line impedance and induce intermittent bus communication faults.