Keri Systems Card Replacement — Compatible K-format, MS & NXT

Keri Systems Compatible Credentials

Keri Systems controllers — including the long-running PXL series and the current Doors.NET platform — accept credentials across two distinct technology generations. The first is the proprietary MS (Megastar) low-frequency proximity format, a 125 kHz protocol Keri developed independently of the commodity 26-bit Wiegand standard. The second is the NXT smart-card line, which builds on genuine NXP MIFARE Classic 1K silicon and carries credential data in a structured MIFARE application. Understanding which technology your panels read is the first step before ordering replacements.

If you are unsure which credential type your installation uses, our card format identification guide walks through the physical markings, reader model numbers, and software settings that distinguish MS prox from NXT smart cards. Both formats are stocked and can be ordered through the same quote workflow, including mixed orders covering both types within a single facility.

Facilities and integrators already familiar with the Keri ecosystem will recognise that the MS format is also used by several other OEM platforms. Our compatible prox cards for AMAG, Lenel, Kantech, and Keri installations covers the overlap where multiple panel brands share the same Wiegand bit structure — useful context if you manage a mixed estate.

K-Format and MS Prox vs NXT MIFARE: What Differs

The MS (Megastar) proximity card operates at 125 kHz and transmits a proprietary bit stream that the Keri reader decodes before passing a standard Wiegand output to the panel. Compatible MS prox credentials reproduce this modulation on T5577 or EM4305 LF carrier chips, which are the established substrates for re-encodable 125 kHz proximity. The resulting card presents an identical signal at the reader antenna — facility code, card number, and parity — without any modification to your controller software or reader firmware.

The Keri NXT-C compatible proximity card represents the smart-card tier of the Keri credential range. NXT cards are built on genuine NXP MIFARE Classic 1K silicon and store credential data in a defined sector structure. Compatible NXT blanks are enrolled by your own Doors.NET system using the same enrolment workflow you already use for OEM cards — the system writes its own keys and application data. This means the security of the credential is determined by your installation's configuration, not by the card source.

For a detailed technical comparison of how the two Keri formats work side by side, see our blog post Keri Systems Cards Explained: K-format, MS / Megastar and NXT.

Encoded to Your System

MS proximity replacements are encoded to order. You supply your facility code, card number range, and — where applicable — the bit-width variant your panels are programmed to accept. We encode each card or fob to that specification before dispatch. No reader or controller changes are required on your end; the replacement credential presents the same data frame as the card it replaces.

NXT smart-card blanks ship in an unenrolled state, formatted and ready for your Doors.NET system to write. This is the correct supply model for AES-secured smart credentials: your controller holds the application keys, and enrolment happens on your hardware. If you operate a managed enrolment service or use a Keri-certified integrator for provisioning, those workflows are unaffected — the blank credential behaves identically to an OEM-sourced blank during the enrolment step.

Our buyer's guide to compatible vs genuine access cards explains this enrolment model in full and addresses common questions about credential interoperability for facilities managers evaluating third-party supply.

Single Replacements and Bulk Supply

Lost or damaged cards in an active installation often need individual replacements on short notice. We supply single cards and fobs at the same per-unit specification as bulk orders — same substrate, same encoding accuracy — so a one-off replacement integrates into your cardholder database without a gap in the number sequence.

For planned upgrades, new-site deployments, or annual credential refreshes, bulk ordering reduces per-unit cost substantially. Our guide to buying compatible access cards in bulk covers quantity thresholds, lead times, packaging options, and how to structure a phased rollout across multiple buildings or access zones. Integrators managing several client sites can consolidate orders for different formats into a single purchase order.

The legacy OEM proximity category covers the broader range of proprietary 125 kHz formats — including Keri MS alongside other manufacturer-specific prox variants — for facilities that need to source replacements across a mixed panel estate. Similarly, the 125 kHz LF proximity cards and fobs category lists the full inventory of compatible LF credentials available to order.

Request a Keri Compatible Card Quote

To request a quote, use the contact form and include your panel model (PXL-250, PXL-500, or Doors.NET version), credential type (MS prox or NXT), facility code, starting card number, and required quantity. If you have an existing card to reference, noting the part number printed on the rear speeds up format confirmation.

We also supply compatible credentials for other access-control platforms commonly installed alongside Keri hardware. If your estate includes Lenel 42-bit compatible cards, Avigilon compatible credentials, or Software House CCOTZ 37-bit compatible cards, those can be included in a single consolidated quote.

Security ID Systems is an independent manufacturer and supplier of compatible access-control credentials and is not affiliated with, authorized by, or endorsed by Keri Systems.