Allen-Bradley 1756-TBCH Terminal Block — ControlLogix RTB Buyer Guide

By Abdullah Zahid
13 min read
Allen-Bradley 1756-TBCH 36-pin screw cage-clamp removable terminal block for ControlLogix 1756 I/O modules

Allen-Bradley 1756-TBCH 36-Pin Screw / Cage-Clamp Removable Terminal Block for ControlLogix I/O Modules

If you are building or expanding a ControlLogix system and need to confirm you have the right removable terminal block before finalizing your BOM, this review is written for you. The Allen-Bradley 1756-TBCH is a 36-pin screw / cage-clamp removable terminal block (RTB) that plugs onto the front of compatible 1756-series I/O modules, providing the physical wiring interface between field devices and the I/O card — while allowing the module to be swapped out without touching a single field conductor. The purchase decision is straightforward once you have confirmed pin count, clamp style, and module compatibility.

If you have already confirmed this is the right part, check current pricing and availability at LeadTime.ca — ships worldwide.

Who Should Buy the 1756-TBCH — and Who Shouldn't

The 1756-TBCH is the right choice when all of the following are true for your application:

  • Your specific 1756 I/O module documentation calls for a 36-pin RTB with standard housing — not a 20-pin or specialty block.
  • Your plant or project standard specifies screw / cage-clamp terminations — not spring-clamp.
  • Your field wiring uses copper conductors within the supported range of approximately 22–14 AWG (single) or 22–16 AWG (double).
  • You are working with a ControlLogix 1756 chassis-based system — not CompactLogix, MicroLogix, or any non-1756 platform.
  • You need a standard-depth housing that fits the wiring arm configuration in your enclosure.

If your I/O module calls for a spring-clamp RTB, the 1756-TBNH is the correct alternative. If your module requires a 20-pin or specialty RTB, the 1756-TBCH will not fit the application regardless of clamp preference. Always verify against the module's installation documentation before ordering.

On this page:

What the 1756-TBCH Actually Does in a ControlLogix System

The Allen-Bradley 1756-TBCH is not an I/O module — it is the removable wiring interface that sits between your field conductors and the 1756 I/O card. Rockwell documentation identifies it as a 36-pin removable terminal block used to provide a modular wiring interface for compatible 1756 I/O modules, ordered separately from the I/O card itself. That last point matters more than it sounds: the RTB does not ship with the module, and missing it from the BOM is one of the most common project delays controls engineers report.

The screw / cage-clamp design gives technicians the ability to re-torque connections during routine maintenance and visually verify that each conductor is fully seated — something experienced electricians consistently cite as a practical advantage over spring-clamp alternatives in high-vibration or high-maintenance environments. The standard housing depth fits the majority of ControlLogix analog and digital I/O modules that use 36-pin RTBs, making the 1756-TBCH a natural default choice for plants standardizing their wiring approach across multiple chassis.

The 1756 ControlLogix platform supports a wide range of I/O modules and removable terminal blocks, allowing modular and flexible wiring for applications from high-speed digital control to process I/O — and the 1756-TBCH covers the broadest cross-section of that module range. Critically, the RTB has no integrated protection devices; external fusing or circuit protection is required per circuit, as specified in the individual I/O module documentation.

Typical ControlLogix System Architecture With an RTB

The 1756-TBCH sits at the front edge of the I/O module, acting as the detachable field-wiring termination point in the ControlLogix signal chain. Here is where it fits in a typical deployment:

  • ControlLogix controller (1756 CPU) in the chassis communicates with I/O modules over the backplane.
  • 1756 I/O modules occupy slots in the 1756 chassis and handle digital or analog signal processing.
  • The 1756-TBCH plugs onto the front face of the I/O module, providing the 36-pin terminal interface where field cables land.
  • Field devices — sensors, actuators, transmitters, or valve positioners — wire directly to the screw / cage-clamp terminals on the 1756-TBCH.
  • When an I/O module needs replacement, the 1756-TBCH detaches with all field wiring intact, the module swaps, and the RTB re-latches onto the replacement card — no field rewiring required.

Typical Applications and Deployment Scenarios

The 1756-TBCH appears in virtually every industry that runs ControlLogix-based control systems. In manufacturing environments — automotive assembly, food and beverage processing, consumer goods packaging — it is the standard wiring termination for I/O racks where technician access and fast module swaps during production shutdowns are a priority.

Process industries including water and wastewater treatment, chemical processing, and mining rely on ControlLogix for continuous process I/O, and the 1756-TBCH is frequently the RTB of choice where multi-channel analog modules require a consistent, re-torqueable wiring interface across multiple cabinets.

OEM machine builders and system integrators who standardize on ControlLogix across their product lines use the 1756-TBCH as a default BOM line item, knowing that a consistent RTB type simplifies spare parts management and technician training across customer sites. Maintenance supervisors at multi-plant facilities particularly value this standardization — a single RTB type stocked in the maintenance crib covers the majority of ControlLogix I/O wiring needs.

Retrofit and upgrade projects also benefit from the 1756-TBCH when aging RTBs show signs of terminal wear from repeated wiring changes, allowing the wiring interface to be refreshed without touching the I/O module or field conductors simultaneously.

Application Typical Deployment
Greenfield manufacturing panel New ControlLogix I/O rack with 1756-TBCH specified as standard RTB on all 36-pin modules
Process plant I/O marshalling Multi-channel analog input/output cards wired to field transmitters and control valves via 1756-TBCH
MRO spare parts inventory Stocking 1756-TBCH units per chassis to enable fast module replacement without production interruption
OEM machine build standardization Single RTB catalog number across all ControlLogix machine variants to simplify BOM and service kits
Panel retrofit / upgrade Replacing worn or damaged RTBs in existing ControlLogix cabinets while preserving field wiring
System integrator ControlLogix build Specified in engineering BOM alongside 1756 I/O modules as a separate line item for each module slot

Key Specifications and Variant Comparison for the 1756-TBCH

Parameter Value Notes
Catalog Number 1756-TBCH Allen-Bradley (Rockwell Automation)
Product Type Removable terminal block (RTB) Wiring accessory — ordered separately from I/O module
Pin Count 36-pin Verify I/O module documentation for required pin count
Clamp Type Screw / cage-clamp Re-torqueable; not interchangeable with spring-clamp RTBs
Housing Style Standard housing (wiring arm) Not extended or fused housing
Wire Size — Single Conductor Approx. 22–14 AWG copper Copper conductors only; verify with Rockwell manual
Wire Size — Double Conductor Approx. 22–16 AWG copper Copper conductors only; verify with Rockwell manual
Operating Temperature Approx. 0–60 °C (32–140 °F) Typical ControlLogix environment; verify official spec
Integrated Protection None Requires external protection per circuit per module documentation
Compatible Platform ControlLogix 1756 I/O only Not for CompactLogix, MicroLogix, or non-1756 families

Full technical specifications are available on the product page at LeadTime.ca.

1756-TBCH vs. 1756-TBNH: Which RTB Do You Actually Need?

Feature 1756-TBCH 1756-TBNH
Clamp Type Screw / cage-clamp Spring-clamp (tool-less insertion)
Pin Count 36-pin 36-pin
Housing Style Standard Standard
Wiring Maintenance Screw torque required; re-torqueable Tool-less; spring holds conductor
Vibration Resistance Good with correct torque Inherently vibration-resistant design
Preferred By Plants and OEMs standardized on screw terminations Facilities requiring tool-less or vibration-resistant wiring
Platform Compatibility ControlLogix 1756 I/O (36-pin modules) ControlLogix 1756 I/O (36-pin modules)

If your plant standard or I/O module specification calls for spring-clamp terminations, the 1756-TBNH is the correct choice over the 1756-TBCH — check current availability of both variants at LeadTime.ca.

Expert Verdict: Is the 1756-TBCH the Right RTB for Your Project?

The 1756-TBCH earns its place as the default ControlLogix RTB choice for a clear reason: it covers the majority of 36-pin 1756 I/O modules, uses a screw / cage-clamp termination that technicians can inspect, re-torque, and verify visually, and behaves exactly as expected across analog and digital I/O applications in manufacturing, process, and heavy industry environments. The buyer profile this fits best is the controls engineer or panel shop specifying ControlLogix hardware where screw termination is the plant or OEM standard — whether for a greenfield build, a chassis expansion, or standardizing spare parts across multiple sites.

Where the 1756-TBCH is genuinely the wrong choice, the answer is usually one of three situations: the I/O module requires a 20-pin or specialty RTB rather than a 36-pin block; the facility has standardized on spring-clamp terminations for vibration resistance or tool-less maintenance workflows, in which case the 1756-TBNH is the correct specification; or the project is not on the ControlLogix 1756 platform at all — CompactLogix, Micro800, and other families use different accessories entirely and the 1756-TBCH will not be compatible. Being honest about these limits is more useful to a buyer than overstating what any single accessory can do.

From a procurement standpoint, the 1756-TBCH is a commonly stocked Rockwell accessory with predictable availability at North American distributors, but lead times can shift depending on regional inventory and order volume. The single most important procurement action before ordering is confirming the RTB type and pin count against the exact 1756 I/O module documentation — a step that takes minutes and prevents the wrong-part delays that extend commissioning timelines. For buyers who want that verification done before committing to a purchase order, view current pricing and stock status at LeadTime.ca and connect with a specialist who can cross-check your module list against the correct RTB variants.

For volume pricing or to confirm lead time before committing to a build, contact the LeadTime.ca team directly — we ship worldwide.

What Engineers Need to Know Before Ordering the 1756-TBCH

Community feedback across forums including PLCTalk, Reddit r/PLC, and distributor Q&A sections consistently reflects the same themes around ControlLogix RTBs: the hardware itself draws minimal complaints, but the ordering process generates a disproportionate share of project headaches. The most common thread is engineers discovering mid-installation that the RTB they ordered does not match the module in hand — either the wrong clamp style or the wrong pin count. Confusing the 1756-TBCH with the 1756-TBNH is the most frequently cited swap error, particularly for engineers newer to ControlLogix who do not yet have a tactile sense of which termination style each module family uses. The practical fix is always the same: open the module's installation document and read the recommended RTB catalog number before placing the order.

A second recurring issue raised by experienced integrators and maintenance technicians is the assumption that I/O modules ship with RTBs included. They do not. The 1756-TBCH is always a separate line item, and forgetting it creates last-minute rush orders that compress installation schedules. Veterans of ControlLogix builds treat the RTB count — one per module plus a maintenance spare buffer — as a mandatory BOM audit step before any purchase order is submitted. Technicians also note that repeated wiring changes or over-tightened screws can wear individual terminals over time, making it worth inspecting RTBs during planned maintenance shutdowns and keeping a small stock on the shelf rather than waiting for a terminal failure to force an emergency order.

Because model-specific community discussion for individual RTB part numbers is limited relative to the broader ControlLogix ecosystem, buyers working through an unfamiliar module combination or a plant with mixed RTB standards are best served by talking to a specialist distributor who can validate the compatibility match before the order goes in. That conversation takes less time than a wrong-part return, and it is exactly the type of pre-purchase check that separates an organized commissioning from an extended one.

Wiring and Installation Overview for the 1756-TBCH

The following points summarize the key requirements for wiring and installing the 1756-TBCH. For full procedures, refer to the Rockwell Automation installation instructions for the specific 1756 I/O module and RTB.

  • Use copper conductors only, within the supported wire size ranges of approximately 22–14 AWG (single conductor) or 22–16 AWG (double conductor); verify exact ranges in the current Rockwell technical data before wiring.
  • De-energize all circuits feeding the I/O before wiring or re-terminating conductors on the 1756-TBCH; verify absence of voltage before working on terminals.
  • Strip each conductor to the manufacturer-recommended length, insert fully into the appropriate screw / cage-clamp terminal, and tighten to the specified torque — approximately 0.5 Nm (4.4 lb-in) — without over-tightening, which can damage the conductor or clamp body.
  • Align the 1756-TBCH with the front face of the I/O module, engage the latching mechanism fully, and confirm visual and tactile seating before restoring power; a partially seated RTB is a common source of intermittent channel faults.
  • Label all conductors and verify terminal assignments against the I/O module's channel map and wiring diagram before commissioning; the 1756-TBCH has no integrated protection, so correct external circuit protection must be in place per the module documentation before energizing.

Wrong-Part Prevention Checklist Before You Order the 1756-TBCH

Run through every item on this checklist against your specific module documentation before placing an order — skipping any one of these is where wrong-part orders originate:

  1. Confirm the exact 1756 I/O module catalog number and verify the recommended RTB type and pin count in the module's installation instructions or technical data.
  2. Verify that you specifically need the 36-pin standard housing RTB; do not use for modules that require 20-pin or specialty RTBs.
  3. Confirm clamp style: 1756-TBCH is screw / cage-clamp – do not order if the specification or plant standard calls for spring-clamp RTBs.
  4. Check required wire size range and ensure it matches plant wiring standards (typical 22–14 AWG single, 22–16 AWG double copper conductors).
  5. Verify quantity: one RTB is needed per I/O module, plus spares for maintenance.
  6. Ensure ControlLogix platform and chassis are specified (this RTB is not for CompactLogix or MicroLogix families).

If any item on this list raises a question about your specific module combination, contact the LeadTime.ca team before ordering — we can cross-check your BOM against the correct RTB variants and confirm real-time availability worldwide.

Frequently Asked Questions

How do I confirm whether my 1756 I/O module requires a 1756-TBCH or a different RTB entirely?

Open the installation instructions or technical data sheet for your specific 1756 I/O module catalog number and locate the recommended RTB section. The document will identify the exact RTB catalog number and pin count required. Do not assume all 1756 modules use the same RTB — some require 20-pin blocks or specialty RTBs, and installing the wrong type will prevent proper connection.

What is the practical difference between the 1756-TBCH and the 1756-TBNH, and does the choice matter?

Both are 36-pin RTBs with standard housing for the same range of ControlLogix 1756 I/O modules, but the 1756-TBCH uses screw / cage-clamp terminations while the 1756-TBNH uses spring-clamp terminations. The choice matters for maintenance practice: screw terminations allow re-torquing and visual verification, while spring-clamp connections are tool-less and inherently vibration-resistant. Mixing types across a plant creates inconsistency in maintenance procedures, so the decision should be governed by your plant's documented wiring standard.

What wire sizes and conductor types are compatible with the 1756-TBCH?

The 1756-TBCH supports approximately 22–14 AWG for single copper conductors and approximately 22–16 AWG for double copper conductors. Copper conductors are required — do not use aluminum wiring. Verify the exact wire size range and strip length in the current Rockwell installation document for your specific module before wiring.

Can I re-use an existing 1756-TBCH when replacing a failed I/O module, or should I replace the RTB at the same time?

In most cases, an undamaged 1756-TBCH with intact terminals and conductors can be transferred directly to a replacement I/O module — this is precisely the modularity the RTB design provides. Inspect the terminals for discoloration, cracking, or signs of wear from repeated wiring changes before re-using. If terminals show mechanical damage or individual clamps no longer hold conductors reliably, replace the RTB alongside the module rather than risk intermittent faults after commissioning.

Do 1756 I/O modules ship with RTBs included, or is the 1756-TBCH always a separate order?

The 1756-TBCH is always a separate line item on the BOM — I/O modules do not include RTBs in the box. This is one of the most frequently reported BOM omissions in ControlLogix project orders. Budget one 1756-TBCH per I/O module slot plus a maintenance spare buffer, and confirm the RTB line items are present in the purchase order before it is submitted.

How many 1756-TBCH terminal blocks do I need for a fully populated ControlLogix chassis?

One RTB is required for each I/O module that uses a 36-pin screw / cage-clamp RTB. A 13-slot chassis with 12 I/O modules, for example, requires 12 RTBs minimum — not counting controller, power supply, or communication module slots, which use different accessories. Add maintenance spares based on your plant's criticality standards; most maintenance planners carry at least one spare per chassis or per module type in use.

Why Order the 1756-TBCH From LeadTime.ca

  • LeadTime.ca ships Allen-Bradley ControlLogix accessories worldwide — not restricted to any single region or country.
  • Specialist team can cross-check your 1756 I/O module list against the correct RTB variants before the order goes in, reducing wrong-part returns.
  • Real-time inventory visibility across North American stock locations with clear lead time communication for items not immediately on the shelf.
  • Volume pricing available for project orders and MRO blanket agreements — contact directly for current rates.
  • Hard-to-find or short-lead-time parts sourced proactively through established distributor channels.

At-a-Glance Summary: Allen-Bradley 1756-TBCH

  • 36-pin removable terminal block (RTB) for ControlLogix 1756-series I/O modules — ordered separately from the I/O module itself.
  • Screw / cage-clamp termination style — re-torqueable and visually verifiable; not interchangeable with spring-clamp RTBs such as the 1756-TBNH.
  • Supports approximately 22–14 AWG single and 22–16 AWG double copper conductors — copper only.
  • Standard housing depth — not an extended or fused housing variant.
  • Operating temperature approximately 0–60 °C (32–140 °F); no integrated protection devices — external circuit protection required.
  • Compatible with ControlLogix 1756 platform only — not for CompactLogix, MicroLogix, or non-1756 families.
  • One RTB required per I/O module; spares recommended for maintenance inventory.
  • Always verify RTB type and pin count against the specific 1756 I/O module documentation before ordering.
  • Pricing and current stock status available on the 1756-TBCH product page at LeadTime.ca.

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