Description
Product Introduction & Engineering Value
The Allen-Bradley 2706-D21J2 is a compact industrial message display intended for PLC-controlled operator prompts, machine status, alarms, troubleshooting instructions, and production information. Its 14-segment VFD provides 16 characters on each of two lines, making it suitable for applications where a simple text display is preferable to a full graphical HMI.
The unit operates from 12–24 VDC and supports serial or parallel message triggering. Its 2K-byte EEPROM stores up to 94 message blocks, allowing frequently used messages to remain resident in the display rather than being continuously transmitted from the controller.
Technical Specifications
| Specification | 2706-D21J2 |
|---|---|
| Series | DL5 Dataliner |
| Display | Vacuum fluorescent |
| Character technology | 14-segment |
| Number of lines | 2 |
| Characters per line | 16 |
| Character set | Uppercase alphanumeric and punctuation |
| Memory | 2K-byte EEPROM |
| Message capacity | 94 message blocks |
| Supply voltage | 12–24 VDC |
| Maximum steady-state current | 250 mA at 12 VDC |
| 24 VDC operating current | Approximately 125 mA |
| Inrush current | Approximately 300 mA |
| Parallel input voltage | 5–24 VDC |
| Parallel inputs | 16 data inputs + port-select input |
| Serial communication | RS-232 |
| Triggering | Serial or parallel |
| Viewing distance | Up to approximately 3 m / 10 ft |
| Operating temperature | 0–50°C |
| Relative humidity | 5–95%, non-condensing |
| Dimensions | 79.3 × 159 × 109 mm |
| Approx. shipping weight | 1.35 kg |
| Enclosure rating | UL Type 12 and Type 13; designed for Type 4 |
| Hazardous-location certification | Class I, Division 2, Groups A, B, C, D |
The published DL5 specification also identifies 5–24 VDC as the parallel-port input range and describes the display as suitable for panel mounting in industrial environments.
Field Application & “Trench” Experience
A common installation pattern for the 2706-D21J2 is a legacy PLC-controlled machine where the controller sends a message number or trigger rather than continuously generating operator text.
For example, a packaging machine can use predefined messages such as:
MACHINE READYCHECK GUARDLOW MATERIALMOTOR OVERLOADPRESS STARTCALL MAINTENANCE
The DL5 retrieves the corresponding stored message when the appropriate trigger is received. This reduces the amount of text-handling logic required in the PLC and keeps the operator interface extremely simple.
Niche Applications
Legacy PLC operator stations
Useful where an existing Allen-Bradley PLC installation was designed around DL5 message displays and replacing the entire HMI would introduce unnecessary engineering work.
Machine status indication
The two-line format is well suited to short status and fault messages where graphics, trends, and touch input are not required.
Maintenance and troubleshooting prompts
Resident messages can provide step-by-step operator or maintenance instructions without requiring a Windows-based HMI.
2706-D21J2
2706-D21J2
Transparency SOP: QA & Testing
For a replacement 2706-D21J2, procurement should distinguish between factory-original stock, new surplus, refurbished equipment, and repaired units.
Recommended receiving inspection:
- Catalog number verification — Confirm the nameplate reads exactly
2706-D21J2. - Revision verification — Published inventory records identify Series A, Series B, and Series X variants, so the installed revision should be recorded before replacement.
- Display test — Verify both 16-character lines illuminate correctly with no missing segments.
- Power test — Apply the required DC input and check current draw against expected values.
- Communication test — Verify RS-232 programming/trigger operation where required.
- Parallel-input test — If the application uses parallel triggering, verify each required input.
- Memory test — Confirm stored messages can be selected and displayed correctly.
- Mechanical inspection — Check the terminal connections, housing, display window, and mounting hardware.
- Application test — Validate actual PLC trigger commands rather than relying only on a powered-display test.
For New Surplus inventory, request photographs of the actual nameplate and revision before purchase. “New” does not by itself establish that the unit is the exact revision required by an existing installation.
Veteran’s Tech Trap Guide
Trap 1 — Confusing 2706-D21J2 with 2706-D21J8
These are not memory-equivalent models.
- 2706-D21J2: 2K EEPROM, 94 message blocks
- 2706-D21J8: 8K EEPROM, 387 message blocks
The two models share the two-line/16-character-per-line format, but the memory capacity is different.
PRO TIP: If the existing application contains a large message library, do not assume a D21J2 can substitute for a D21J8 simply because the physical display format looks identical.
Trap 2 — Assuming serial and parallel operation are simultaneous
The 2706-D21J2 provides serial and parallel triggering capability, but the published technical description indicates the two interfaces are selected rather than operated simultaneously.
PRO TIP: Check the DIP-switch configuration and the original PLC interface wiring before commissioning the replacement.
Trap 3 — Ignoring the exact display revision
The 2706-D21J2 exists in multiple revisions, including Series A and Series B listings.
For a legacy machine, revision differences can matter more than the catalog number printed in an old spare-parts list.
PRO TIP: Photograph the existing nameplate, terminal layout, and revision marking before placing a replacement order.
Dynamic FAQ
Is Allen-Bradley 2706-D21J2 a PanelView HMI?
No. It is a DL5 Dataliner message display, not a modern graphical PanelView terminal. It is intended primarily for predefined text messages and operator status information.
How many characters can the 2706-D21J2 display?
It provides two lines with 16 characters per line. The display uses 14-segment VFD technology.
How much message memory does the 2706-D21J2 have?
The D21J2 contains 2K bytes of EEPROM and supports up to 94 message blocks.
What power supply does it require?
The published DL5 specifications identify a 12–24 VDC supply. The parallel input interface accepts 5–24 VDC.
Is 2706-D21J8 a direct replacement?
Not automatically. The D21J8 is also a two-line DL5, but it provides 8K-byte memory and up to 387 message blocks, compared with 2K/94 for the D21J2. Application memory requirements and the installed revision should be checked before substitution.
What should I verify when buying New Surplus 2706-D21J2?
Verify the exact catalog number, series/revision, physical condition, display operation, memory operation, and communication interface. For New Surplus authenticity, request an actual-unit nameplate photograph and packaging/label information rather than relying only on a stock photograph. Warranty terms should also be stated separately from any original Rockwell factory warranty.
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