The AB_KT-1 driver is the RSLinx Classic path that binds a KT-series ISA interface card to a Data Highway Plus trunk. It remains the practical programming route for many PLC-5 and SLC 500 lines that never received Ethernet sidecars. The driver is tightly coupled to 1784-KT, 1784-KTX, and 1784-KTX-D hardware; treating a PKTX or U2D/U2HP USB adapter as if it were a KT card simply yields an empty Available Drivers list or an Error state.

One ISA card, one AB_KT-1 instance, one unique octal DH+ node—then patch RSLinx before any production download on 2.50 media.

Supported cards and non-supported cousins

1784-PCMK, 1784-PKTX, and 1784-U2HP are not AB_KT-1 devices. They require their own driver entries and their own DH+ node numbers.

RSLinx versions and KB33885

AB_KT-1 ships with CPR7 through CPR10-era RSLinx Classic builds commonly used on Windows XP and later legacy hosts. RSLinx 2.50.00 (CPR9 SR2) is a special case: Knowledgebase 33885 documents that unpatched AB_KT-1 downloads can corrupt PLC logic—rungs appearing to revert, forces flipping, or subroutines resolving to the wrong addresses after a download that looked clean. Install the KB33885 patch or move to 2.51+ before writing to a production PLC-5. Verify Rslinx.exe version after patching; a failed patch can leave the UI at 2.50 while the DH+ download path remains unfixed.

Hardware and BIOS preparation

1. Power down the XP (or legacy) workstation and insert the KT/KTX card in a free ISA slot.
2. Land the three-pin Phoenix DH+ tap with correct polarity: blue high, black low, clear/shield drain.
3. Set bracket rotary switches to a unique octal node (0–77) not already on the trunk.
4. In BIOS, reserve a free IRQ (often 5, 7, 9, 10, or 11) and an I/O base such as 0x300; set PnP OS = No for ISA.
5. Boot Windows. The Found New Hardware wizard may fail—that is expected; RSLinx supplies the SST binding.

Binding AB_KT-1 in RSLinx

Install RSLinx Classic, reboot, then open Communications → Configure Drivers. Add AB_KT-1 (DH+), name the instance, select the detected ISA card, and match the node address to the rotary switches. A green Running state means the card initialized; yellow often means the card is alive but no peer traffic is seen yet. SST source 1001 events with sub-code 0x0A indicate IRQ conflict; 0x0B indicates I/O base conflict.

Verification and troubleshooting

Expand the driver in RSWho and confirm every PLC-5, SLC, and PanelView node appears within a few seconds. Driver Diagnostics should show Good Tx / Good Rx counts incrementing. From RSLogix 5, browse the path rooted at AB_KT-1 and run a read-only verify before any download. Empty RSWho usually means reversed DH+ polarity, missing termination (150 Ω at both physical ends), baud mismatch, or a duplicate octal node. Corruption after an apparently successful download on 2.50 media points back to KB33885, not to the ladder.

New Windows 10/11 benches should migrate to 1784-U2HP, Ethernet gateways, or ControlLogix bridging rather than forcing ISA. Until that cutover, keep a known-good KT/KTX card and patched RSLinx image with other PLC and PAC communications assets.