RAD S-TAU Trunk Access Unit

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RAD S-TAU Trunk Access Unit 


  • S-TAU, Smart Trunk Access Unit, provides direct physical and electrical connection between workstations and the Token Ring network. Functioning as a passive wiring concentrator, S-TAU offers star-shaped ring topology for eight users. For larger networks, several S-TAUs can be linked together by connecting Ring In/Ring Out expansion ports.
  • Insert and bypass functions are provided within the unit. Insertion of a workstation into the ring occurs when the workstation's network interface card or adapter provides a DC current across the lobe cable to the lobe port of S-TAU. The station only accesses the ring if the adapter and cable are fully operational.
  • Each lobe is equipped with a status LED indicator, indicating that a station is actively inserted into the ring, thus simplifying diagnostics and troubleshooting. Bypassing of a lobe occurs automatically whenever the lobe cable connection is removed or the station becomes inactive or exits the network.
  • Several options are available for installation at either the Ring In (RI) or the Ring Out (RO) ports. These include:
    • TFCs, Fiber Optic Converters, which allow fiber connection between adjacent S-TAUs, or enable lobe connection of S-TAU using fiber.
    • TFRs, Fiber Optic Repeaters, which extend the distance between adjacent S-TAUs to 3 km.
    • TCRs, Copper Repeaters, which extend the distance between adjacent S-TAUs to 750m on Type 1 cable.
  • S-TAU operates without external power. However, an external power supply is required for each RI or RO option above (see Ordering).
  • S-TAU is installed in a 19" rack mount enclosure. The unit height is only 1U (1.75"), requiring minimal rack space.
  • The standard S-TAU is provided with IBM data connectors for use in an IBM cabling environment. Optionally, RJ-45 connectors can be supplied, for connection of Unshielded Twisted Pair (UTP), while retaining the self-shorting (bypass) feature.
  • To ensure proper operation of S-TAU, a TST pre-installation setup tool should be used. This small universal tool should be ordered separately.


  • Compatible with IBM Token Ring at 4 or 16 Mbps
  • Complies with IEEE 802.5 standard
  • No external power required
  • Lobe insertion LEDs
  • Supports 8 workstations
  • Optional built-in repeaters
  • 1U height for minimal rack space
  • RJ-45 or IBM data connectors

Trunk Access Unit

+ Specify Ring In option:
IF16 for TFR Fiber Optic Repeater
IC16 for TCR Copper Repeater
IT for TFC Fiber Optic Converter
$ Specify Ring Out option:
OF16 for TFR Fiber Optic Repeater
OC16 for TCR Copper Repeater
OT for TFC Fiber Optic Converter
& Specify connector type:
RJ45 for RJ-45 connector
(Default is IBM data connector)

Note: All RI/RO options require PS-115/7.5/800 or PS-230/7.5/800 power supply.


115 VAC power supply (for all RI/RO options)

230 VAC power supply (for all RI/RO options)

Pre-installation Setup Tool

Pre-installation Setup Tool for S-TAU with adapter cable for RJ-45 connectors

Note: One TST tool may be used for any number of S-TAUs.

Type-3 Media Filter





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