1492 IFM Modules & Pre-Wired Cables: System Overview, Catalog Decode, Selection & Wiring
The Allen-Bradley Bulletin 1492 wiring system replaces conventional point-to-point wiring between a PLC I/O module and field terminal blocks with two pre-engineered pieces: an interface module (IFM) mounted on a DIN #3 rail, and a pre-wired, pre-tested cable (1492-CAB) that plugs the I/O module directly into the IFM. Field wiring lands on the IFM's larger, more accessible terminals instead of on the I/O module itself. According to Rockwell publication 1492-TD008, the wiring system can be installed up to 30 times faster than traditional point-to-point wiring, and the cables are 100% tested for continuity to eliminate point-to-point checking. This guide explains what an IFM is, how to decode a 1492-CAB cable catalog number, the IFM module types, the 1492-W feed-through terminal blocks, and how to select the right IFM and cable for a given I/O module — all sourced directly from the manufacturer datasheets.
Contents
1. What Is the 1492 Wiring System?
Unlike conventional terminal blocks, the Bulletin 1492 wiring system connects to both digital and analog PLC I/O modules through pre-wired and pre-tested cables. The interface modules (IFMs) are mounted onto a standard DIN #3 rail. Pre-printed adhesive label cards containing field-wiring information are included for each interface module and I/O module combination.
The system has two core components that work together:
- The pre-wired cable (1492-CAB). One end plugs onto the PLC I/O module (via a removable terminal block, wiring arm, or D-shell connector that matches the module); the other end has a keyed connector that plugs into the IFM. The cable carries every I/O point and the module power connections.
- The interface module (IFM). A DIN-rail-mounted module that breaks the cable out to high-density, accessible field-side terminals. Field device wires (sensors, actuators) land here — not on the I/O module. IFMs are available with field-side status LEDs, fuse clips, and relays.
Why Use It Instead of Point-to-Point Wiring?
Publication 1492-TD008 lists these documented benefits:
| Benefit | Detail |
|---|---|
| Reduced wiring time | PLC I/O-to-field-device wiring completes in a fraction of the time vs. traditional point-to-point wiring |
| Reduced wiring errors | Cables are pre-tested for 100% accurate connections, eliminating point-to-point checking |
| Faster troubleshooting | Fuses, blown-fuse indication, and field-side ON-state LEDs let maintenance locate faults quickly |
| Increased volume / productivity | Wiring system can be up to 30 times faster to install than traditional point-to-point wiring |
| Reduced wire prep | Eliminates the time and cost of stripping and cutting wires; route one cable versus 20–40 conductors |
| Labeling and marking | Pre-printed, PLC-I/O-specific adhesive label strips replace labor-intensive wire markers |
| Simplified design | Engineers call out an IFM and cable instead of detailing every wire and terminal block |
| Increased DIN rail density | DIN rail space can be reduced by more than 50%; narrow IFMs available for further savings |
Which Platforms Are Supported?
Bulletin 1492 wiring systems are available for 1756 ControlLogix, 1769 CompactLogix, 1769 CompactLogix 5370, 1746 SLC 500, and 1762/1764 MicroLogix I/O. A select group also supports the MicroLogix 1200 (40-I/O base only) and 1500 packaged controllers, plus 1794 FLEX I/O through the D-shell FLEX base modules. A separate publication, 1492-TD018, covers the 5069 Compact 5000 / CompactLogix platform.
2. How to Order a 1492 Wiring System
To order the proper IFM/XIM/AIFM and pre-wired cable, publication 1492-TD008 walks through four decisions:
- Determine the I/O platform and module. Identify the PLC or PowerFlex I/O platform (e.g., Bulletin 1746, 1756, 1757, 1762, 1764, 1769, 1794, 700H, 700S) and the catalog number of the specific I/O module being wired (for example, 1769-OB16).
- Determine your diagnostic and power needs. Decide whether you require field-side LEDs, fusing for over-current protection, or relays. Check voltage ratings for the LEDs, blown-fuse indication, relay contacts, and coil voltage.
- Determine field-side wiring requirements. Decide whether you need extra terminals (two or more field-side terminals per I/O point, e.g., to land device commons in-panel).
- Determine the cable length. Choose the I/O-module-to-IFM cable length: 0.5 m, 1.0 m, 2.5 m, 5.0 m, or a build-to-order length.
Note: A removable-terminal-block (RIFM) version of many IFMs is available. If selected, the terminal plugs (RTB) must be ordered separately — two plugs per catalog number — in screw or push-in style.
3. Pre-Wired Cable (1492-CAB): Catalog Number Decode
The pre-wired cable replaces the point-to-point wiring between an Allen-Bradley I/O module and individual terminal blocks. It has a removable terminal block or wiring arm at the I/O end and a keyed cable connector at the IFM end, uses #22 AWG wire, and is 100% tested for continuity. The catalog number encodes the length and the cable type (which fixes the I/O-module-end connector).
Decoding 1492-CAB020E69
| Segment | Meaning | Value in 1492-CAB020E69 |
|---|---|---|
| 1492 | Bulletin | Programmable Controller Wiring Systems |
| CAB | Product type | Pre-wired cable |
| 020 | Length code | 2.0 m (6.56 ft) — build-to-order length |
| E69 | Cable type | Identifies the I/O-module-end connector and the keyed IFM-end connector |
Length Codes
To order a pre-wired cable, insert the length code in place of the asterisks shown in the IFM selection charts (e.g., 1492-CAB***E69):
| Code | Length | Type |
|---|---|---|
| 005 | 0.5 m (1.64 ft) | Standard |
| 010 | 1.0 m (3.28 ft) | Standard |
| 025 | 2.5 m (8.20 ft) | Standard |
| 050 | 5.0 m (16.40 ft) | Standard |
| 001–020 | 0.1–2.0 m (0.328–6.56 ft), in 0.1 m increments | Build-to-order |
| 020–100 | 2.0–10.0 m (6.56–32.8 ft), in 0.5 m increments | Build-to-order |
| 100–300 | 10.0–30.0 m (32.8–98.4 ft), in 1.0 m increments | Build-to-order |
The “26” AWG Suffix
Standard 1492-CAB cables use 22 AWG wire rated at 2 amps per I/O channel. A more flexible 26 AWG version is available with a limit of 1 amp per I/O channel — add “26” to the end of the catalog number (example: 1492-CAB***F69 becomes 1492-CAB***F6926).
Cable Type Code (the E69 Suffix)
The trailing cable-type code (E69, G69, L69, A94, etc.) fixes which connector lands on the I/O-module end and is matched to a specific group of I/O modules in the selection charts. For the E69 cable:
| Attribute | 1492-CAB***E69 |
|---|---|
| No. of conductors | 20 |
| Conductor size | #22 AWG |
| Nominal outer diameter | 9.0 mm (0.36 in.) |
| I/O-module-end connector | 1769-RTBN18 removable terminal block |
| Example I/O module served | 1769-OB16 (1769 CompactLogix 24V DC source output) |
Confirm the Cable Type Against Your Exact Module
The cable-type code (E69, G69, L69, etc.) is module-specific — it sets the connector that mates to your I/O module. Always cross-reference the IFM selection chart in 1492-TD008 for your exact module catalog number to confirm the correct cable type before ordering. The E69 cable shown here is matched to 1769 CompactLogix modules such as the 1769-OB16.
4. IFM Interface Module Types
Digital IFMs, similar to groups of terminal blocks, are available with either 20-pin (typically 8–16 PLC I/O points) or 40-pin (typically 16–32 PLC I/O points) cable connectors. The number of field-side wiring terminals varies with the module type, from one to three terminals per I/O point. Status indicators, fuse clips, and relays are available on-board to customize the wiring system and assist troubleshooting.
| IFM Type | Field-Side Terminals | Purpose |
|---|---|---|
| Standard (feed-through) | 1 per I/O point + module power | Basic break-out. Ideal when I/O device commons are terminated in the field or remotely from the I/O module panel. |
| Extra Terminal | 2 or 4 per I/O point | Land device commons in the same panel. Non-isolated versions common the lower row in groups of 10 to serve as a power bus; isolated versions group terminals into 8 or 16 isolated groups. |
| Sensor | 3 per input point | Middle and lower rows commoned in groups of 18 form power buses for 3-wire 24V AC/DC sensors (120V AC on IFM20F-3 only). |
| LED Indicating | Same as base type + LEDs | Voltage-indicating LEDs show on/off status of the input device or output circuit for field-side diagnostics. Circuitry works with sinking or sourcing modules. |
| Fusible | 2 or 4 per I/O point | Adds overcurrent protection with onboard 5 x 20 mm fuse clips; available with or without 24V/120V blown-fuse indication. Isolated and non-isolated versions; see-through cover. Fuses not included. |
| Relay Master / Expander (XIM) | Form C relay contacts | Field-replaceable relays with 24V or 120V coils; isolated Form C contacts rated 240V 10 A (de-rated to 12 A per adjacent pair). Coil-side status LED and transient suppression. Masters available in 8 or 16 relays; expanders add 8. |
20-Pin vs. 40-Pin
Match the IFM connector size to the I/O module's point count: a 20-pin IFM serves modules of roughly 8–16 I/O points; a 40-pin IFM serves 16–32 I/O points. The IFMs are compatible with both the pre-wired cables and the IFM-ready cables.
5. Feed-Through Terminal Blocks (1492-W Series)
The 1492-W series are DIN-rail-mounted screw-type feed-through terminal blocks. They are used for general field wiring and to extend or supplement the field-side connections of a 1492 wiring system. Specifications below are sourced from publication 1492-TD015.
Single-Circuit Feed-Through Blocks
| Catalog Number | Voltage Rating | Max Current | Wire Range | Strip Length | Torque |
|---|---|---|---|---|---|
| 1492-W3 | 600V AC/DC (IEC 800V) | 20 A (CSA 24 A) | #30–14 AWG (0.5–2.5 mm²) | 0.39 in. (10 mm) | 5.0–5.6 lb·in (0.6 N·m) |
| 1492-W4 | 600V AC/DC (IEC 800V) | 30 A (CSA 32 A) | #22–10 AWG (0.5–4.0 mm²) | 0.35 in. (9 mm) | 5.0–5.6 lb·in (0.6 N·m) |
| 1492-W6 | 600V AC/DC (IEC 800V) | 40 A (CSA 41 A) | #22–10 AWG (0.5–6.0 mm²) | 0.47 in. (12 mm) | 5.6–6.8 lb·in (0.7 N·m) |
1492-W4TW — Three-Connection Feed-Through Block
The 1492-W4TW is a feed-through terminal block with 3 connection points (2 on one side) — useful where one field circuit must fan out to multiple connections without a separate jumper block.
| Attribute | 1492-W4TW |
|---|---|
| Description | Feed-through terminal block, 3 connection points (2 on one side) |
| Voltage rating | 600V AC/DC (CSA 600V, IEC 800V) |
| Maximum current | 30 A (CSA 20 A, IEC 32 A) |
| Wire range | #18–10 AWG (CSA #22–12 AWG / IEC 0.5–4 mm²) |
| Wire strip length | 0.35 in. (9 mm) |
| Recommended torque | 5.0–5.6 lb·in (0.6 N·m) |
| Housing temperature range | -40…+195 °F (-40…+90 °C) |
1492-W4TW-W Color Variant Not Individually Datasheet-Sourced
The base 1492-W4TW ratings above are taken directly from publication 1492-TD015. The specific variant 1492-W4TW-W (with the “-W” white color suffix) is not listed as an individual catalog entry in 1492-TD015 or 1492-TD008. The “-W” suffix denotes the housing color (white); the electrical and mechanical ratings are those of the base 1492-W4TW. Confirm the color/marking variant against the current Rockwell product profile before quoting.
6. How to Select an IFM + Cable for an I/O Module
Selection always starts from the specific I/O module catalog number, then walks the four ordering decisions. Worked example for a 1769-OB16 (1769 CompactLogix 24V DC source output module):
- Look up the module in 1492-TD008. Find the 1769-OB16 selection chart. The available wiring-system modules and the matching cable type are listed for that exact module.
- Pick the IFM type. For a basic break-out, a feed-through 1492-IFM20F (20-pin, one terminal per point). For field-side LED diagnostics, 1492-IFM20D24. For overcurrent protection, a fusible 1492-IFM20F-F24-2. For relay isolation, an XIM relay master.
- Decide fixed vs. removable terminals. Choose the IFM (fixed terminals) or the RIFM (removable terminal block). RIFM requires separate RTB plugs (e.g., RTB20N screw or RTB20P push-in), ordered two per catalog number.
- Pick the matching cable type. The chart specifies the cable type for that module — for the 1769-OB16 it is the E69 cable (1492-CAB***E69, 20-conductor, 1769-RTBN18 module-end RTB).
- Insert the length code. Choose the cable length and insert the code: e.g., 2.0 m build-to-order gives 1492-CAB020E69; a standard 1.0 m gives 1492-CAB010E69.
| Decision | Example for 1769-OB16 |
|---|---|
| I/O module | 1769-OB16 (16-point 24V DC source output) |
| IFM (feed-through, fixed) | 1492-IFM20F |
| IFM (feed-through, removable) | 1492-RIFM20F + RTB20N (screw) or RTB20P (push-in) plugs |
| Cable type | 1492-CAB***E69 |
| Cable, 2.0 m build-to-order | 1492-CAB020E69 |
Always Verify Against the Module-Specific Chart
Cable type and IFM compatibility are module-specific. The E69 cable and IFM20F shown here are correct for the 1769-OB16 per 1492-TD008, but a different 1769, 1756, 1746, or MicroLogix module may require a different cable type and IFM. Never substitute a cable type across modules — the connector keying and pinout will not match. Confirm the exact catalog numbers in the selection chart for your module.
7. Wiring Specifications & Ratings
These are the general wiring-system specifications for 1492 IFM modules and cables, sourced from publication 1492-TD008.
Terminal Block Wire Range & Strip Length
| Terminal Style | Wire Range (Rated Cross Section) | Wire Strip Length |
|---|---|---|
| Fixed Screw Style | #12–#22 AWG (4.0–0.2 mm²) | 0.32 in. (8.0 mm) |
| Removable Screw Style | #12–#22 AWG (2.5–0.5 mm²) | 0.28 in. (7.0 mm) |
| Removable Push-in Style | #12–#26 AWG (2.5–0.2 mm²) | 0.39 in. (10.0 mm) |
Screw Torque
| Terminal Style | Recommended Torque |
|---|---|
| Fixed Screw Style | 3.5–4.5 lb·in (0.38–0.50 N·m) |
| Removable Screw Style | 3.5–4.5 lb·in (0.38–0.50 N·m) |
| Removable Push-in Style | N/A |
Maximum Wires per Terminal (Fixed Screw Style)
| Max AWG | Max No. of Wires per Terminal |
|---|---|
| #22, #20, #18 | 3 wires |
| #16 | 2 wires |
| #14, #12 | 1 wire |
Note: Maximum number is for the same gauge of stranded copper conductors per wire funnel.
Environmental & Agency
| Parameter | Specification |
|---|---|
| Maximum peak transient voltage | 600V (use a UL Recognized 2.5 kV suppression device above 600V) |
| Operating temperature range | 0…60 °C |
| Operating humidity | 5–95% non-condensing |
| Operating vibration | 2.5 G at 10–2000 Hz |
| Operating shock | 15 G |
| Storage temperature (cables) | -20…+80 °C |
| Storage temperature (modules) | -40…+85 °C |
| Pollution degree | 2 |
| Agency | cULus Hazardous Locations Class I Div 2 Groups A–D (modules without relays); UL File E10314. Modules with relays: cULus Ordinary Locations, UL File E113724. FM Class I Div 2. |
DIN Rail & Current Rating
1492 IFM and AIFM modules mount on a standard DIN #3 rail for quick installation. The field-side terminals accommodate #22–12 AWG wire and carry a continuous current rating of 2 A per circuit, supporting higher-current programmable-controller output modules. Standard 1492-CAB cables (22 AWG) are rated 2 A per I/O channel.
8. Installation Best Practices
Power Off Before Wiring
Always disconnect power to the PLC and field circuits before plugging or unplugging cables, removing IFMs, or landing field wiring. Energized work risks electrical shock, equipment damage, and unintended machine operation.
- Mount the IFM on the DIN #3 rail. Snap the IFM onto a standard DIN #3 rail in your panel. Narrow and reduced-height IFM variants are available where panel space is tight.
- Verify the cable type matches the module. Confirm the 1492-CAB cable-type code (e.g., E69) is the one specified for your exact I/O module in the selection chart. The connectors are keyed; a mismatched cable will not seat correctly.
- Plug the cable onto the I/O module. Connect the cable's I/O-end terminal block, wiring arm, or D-shell connector to the module. D-shell cables include a slide-locking mechanism; press until the locking tabs engage for a secure connection.
- Plug the other end into the IFM. The 20- or 40-pin keyed connector mates to the IFM with locking tabs. Push until it latches.
- Apply the pre-printed label strips. Each IFM + I/O-module combination ships with pre-printed adhesive label cards identifying the field-side terminals. Apply them to speed field wiring and troubleshooting.
- Land field wiring on the IFM terminals. Strip wires to the correct length for the terminal style (fixed screw 8 mm, removable screw 7 mm, push-in 10 mm) and tighten screw terminals to 3.5–4.5 lb·in (0.38–0.50 N·m). Observe the max-wires-per-terminal limits.
- For fusible IFMs, install fuses. Fuses (5 x 20 mm) are not included — install the correct rating for your circuit. Use the see-through acrylic cover and a fuse puller for service.
- For RIFM versions, fit the RTB plugs. Removable-terminal IFMs require separately ordered RTB plugs (screw or push-in), two per catalog number.
Pre-Wire and Pre-Test for Faster Commissioning
Because the cables are factory pre-wired and 100% continuity-tested, and the IFM field terminals are accessible and labeled, you can wire and verify the field side at a bench, then plug the cable onto the I/O module in seconds at the panel. This is the core labor saving that makes the 1492 system up to 30x faster than point-to-point wiring on multi-module panels.
Reference Documentation
The following Rockwell Automation publications were used as references for this guide. These are the official manufacturer documents for the hardware covered in this article.
| Publication | Description | Download |
|---|---|---|
| 1492-TD008 | Programmable Controller Wiring Systems (Bulletin 1492) Technical Data — IFMs and pre-wired cables | |
| 1492-TD015 | Spring-Clamp and Screw-Type Terminal Blocks (1492-W series) Technical Data | |
| 1492-TD018 | 5069 CompactLogix / Compact 5000 Wiring Systems Technical Data |
Need 1492 IFMs, Pre-Wired Cables, or Terminal Blocks?
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