Product Overview

The Allen-Bradley 1794-TB3​ is a screw-type terminal base unit belonging to the Rockwell Automation Allen-Bradley 1794 FLEX I/O product family. It is a passive, non-intelligent wiring base designed to accept any standard 1794-series electronic I/O module (analog, discrete, specialty, or communication) which snaps onto the top of the base and engages a card-edge connector to establish both signal pass-through and module-bus communication. The Allen-Bradley 1794-TB3​ provides 24 screw terminals (arranged as two rows of twelve) for field-device wiring—sensors, actuators, analog transmitters, thermocouples, or serial devices—depending on the electronic module inserted. Unlike the 1794-TB2 (spring-clamp) or 1794-TBN (fewer terminals), the Allen-Bradley 1794-TB3​ uses traditional screw-clamp terminals accepting 14–22 AWG (0.25–2.5 mm²) solid or stranded wire with a typical tightening torque of 0.5–0.6 N·m (4.4–5.3 lb·in), which many panel shops prefer for familiarity and ease of re-tightening during maintenance.The Allen-Bradley 1794-TB3​ itself contains no active electronics, power supply, or communication logic; it purely provides the physical termination points and the mechanical keying that aligns with the selected 1794 module type. It mounts on a standard 35 mm DIN rail (EN 60715) and interlocks with adjacent FLEX I/O bases (such as 1794-TB3 itself under another module, or a 1794-APB / 1794-AENTR adapter base) via the FLEX bus tongue-and-groove connectors, which carry the 5 V backplane logic and, in networked adapters, the fieldbus signals. The Allen-Bradley 1794-TB3​ is color-coded (usually dark gray) and marked with terminal numbers corresponding to the I/O point assignments defined by the mounted electronic module’s datasheet. Its open-top design allows the 1794 module to be removed and replaced—with or without power—without disturbing any field wiring, a key advantage for minimizing downtime during module failure or change-out.Supplied as a fundamental accessory in every FLEX I/O installation, the Allen-Bradley 1794-TB3​ is specified wherever screw-terminal field wiring is mandated by plant standards or where technicians are more comfortable verifying mechanical tightness of screw connections versus spring-clamp types. It is fully compatible with the entire 1794 module catalog, including high-density discrete (1794-IB16, 1794-OB16), analog (1794-IE4XOE2, 1794-IF8), thermocouple (1794-IT8), RTD (1794-IR8), and specialty modules (high-speed counter, ASCII, etc.), making the Allen-Bradley 1794-TB3​ one of the most universally stocked spare parts in FLEX I/O-based automation systems.

Technical Specifications

Product Model | 1794-TB3Manufacturer | Rockwell Automation / Allen-BradleyProduct Type | FLEX I/O Screw Terminal Base Unit (Passive Wiring Base, No Electronics)Number of Terminals | 24 screw terminals (2 rows × 12)Terminal Type | Screw-clamp (slotted head), zinc-plated steel with brass insertWire Size Accepted | 22–14 AWG (0.25–2.5 mm²) solid or stranded (with/without ferrule)Recommended Tightening Torque | 0.5–0.6 N·m (4.4–5.3 lb·in)Rated Voltage (Terminals to Earth/Ground) | 250 V AC/DC (per IEC 60664-1, Pollution Degree 2)Rated Current per Terminal | Depends on inserted module; base itself is passive—current rating follows module spec (typically ≤ 2 A per I/O point for discrete modules)Backplane / FLEX Bus Connection | Through 1794 module edge connector; TB3 provides mechanical alignment & signal routing onlyCompatible Electronic Modules | All standard 1794 series modules (discrete, analog, thermocouple, RTD, HSC, ASCII, etc.)Compatible Adapter / Network Bases | 1794-APB (Profibus DP), 1794-AENTR (EtherNet/IP), 1794-ADN (DeviceNet), 1794-ACN15 (ControlNet), etc.Mounting | 35 mm DIN Rail (EN 60715 Top Hat); tongue-and-groove interlock with adjacent 1794 basesEnclosure Requirement | Install inside IP54 or better enclosure (IP20 module rating)Operating Temperature | 0 °C to +60 °C (+32 °F to +140 °F) — same as 1794 module installedStorage Temperature | -40 °C to +85 °CHumidity | 5 %–95 % RH, non-condensingDimensions (H×W×D) | Approx. 76 × 46 × 62 mm (3.0 × 1.8 × 2.4 in.) excluding DIN rail footWeight | Approx. 55 g (0.12 lb)Certifications / Compliance | UL 508, cULus Listed, CE Marked, RoHS CompliantColor | Dark Gray (standard 1794 family color)

Main Features and Advantages

Universal 1794 Module Compatibility:The Allen-Bradley 1794-TB3​ accepts the full range of 1794 electronic modules—digital, analog, temperature, communication, and specialty—so a single base type can be stocked as a universal spare across an entire FLEX I/O installation. This simplifies MRO inventory and reduces the risk of specifying the wrong base when ordering replacements.Familiar Screw-Clamp Terminals for Field Wiring:Many industrial electricians prefer screw terminals over spring-clamp types because they can be visually inspected for tightness and re-torqued with a standard screwdriver. The Allen-Bradley 1794-TB3​ delivers this familiar interface with clearly numbered terminals that correspond directly to the I/O point designations in the module’s technical data, reducing wiring errors during panel build.Module Hot-Swap Without Disturbing Field Wires:Because the electronic module snaps onto the Allen-Bradley 1794-TB3​ and connects via an edge-card socket, a faulty or upgraded module can be unlatched, lifted off, and replaced while all 24 field wires remain securely terminated in the base. This “wire-once” design is one of the principal value propositions of the FLEX I/O architecture and is fully realized by the Allen-Bradley 1794-TB3.DIN Rail Mounting with Interlocking FLEX Bus:The Allen-Bradley 1794-TB3​ slides onto a standard 35 mm DIN rail and mechanically interlocks with adjacent terminal bases and adapter bases via tongue-and-groove connectors that also carry the 5 V FLEX backplane signals. This creates a rigid, aligned assembly and ensures correct module order without separate mounting hardware. The interlocking system also provides keying to prevent insertion of an incompatible module type in a given base position (where applicable, via module-specific keys).Clear Terminal Numbering and Color Coding:Each terminal on the Allen-Bradley 1794-TB3​ is permanently stamped with its number (1–24), and the base housing is marked with the standard 1794 orientation icon. When a 1794 module is installed, its silkscreen I/O labels align with the terminal row, allowing technicians to quickly trace a field wire from the terminal number back to the logical I/O point in the PLC program—a small but meaningful aid during commissioning and troubleshooting.No Configuration or Commissioning Required:Being a passive wiring base, the Allen-Bradley 1794-TB3​ requires zero software configuration. It is entirely mechanical and electrical in function—simply mount it, land the field wires, snap in the 1794 module, and the system is ready. This eliminates configuration errors and speeds up initial panel checkout.

Application Field

The Allen-Bradley 1794-TB3​ is used wherever Allen-Bradley FLEX I/O is deployed for distributed or rack-based I/O in process, hybrid, and discrete manufacturing automation. In automotive assembly plants, FLEX I/O with the Allen-Bradley 1794-TB3​ base is mounted in IP54-rated local enclosures positioned close to weld-gun banks, conveyor zones, or press-side safety gates—the screw terminals make it straightforward for maintenance electricians to land sensor and solenoid wires on the spot. In food & beverage packaging lines, the Allen-Bradley 1794-TB3​ supports analog modules reading flow-meter 4–20 mA signals and discrete modules driving wash-down-rated pilot valves, with the base’s open-top design allowing quick module swaps during scheduled clean-ups without disconnecting the field wiring.In oil & gas well-pad RTU shelters and water/wastewater lift stations, the Allen-Bradley 1794-TB3​ is paired with a 1794-AENTR EtherNet/IP adapter base to create a compact, panel-mounted I/O cluster that communicates back to a central SCADA or PAC over Ethernet, while the screw terminals accommodate loop-powered 2-wire transmitters and dry-contact inputs from level switches. In batch-process skids (chemical dosing, CIP stations), the Allen-Bradley 1794-TB3​ provides the termination platform for thermocouple and RTD modules (1794-IT8 / IR8) as well as analog output modules controlling variable-frequency pump drives. Because the Allen-Bradley 1794-TB3​ is non-electronic, it is equally at home behind any 1794 module type and is thus a universal staple in MRO stores for plants standardized on FLEX I/O—from the smallest machine cell to the largest process-unit DCS interface.