Dual-Frequency (125 kHz + 13.56 MHz) Compatible Cards

What a Dual-Frequency Card Is

A dual-frequency card — also called a combi card or dual-technology credential — integrates two independent RFID circuits into one card body. The 125 kHz antenna and chip handle all low-frequency proximity reads; the 13.56 MHz antenna and chip handle all high-frequency smart-card reads. Each band operates completely independently: presenting the card to a 125 kHz reader activates only the LF circuit, and presenting it to a 13.56 MHz reader activates only the HF circuit. There is no cross-band communication or interference between the two.

On the low-frequency side, the card carries your existing proximity format — whether that is a standard 26-bit Wiegand payload, a HID Corporate 1000 48-bit facility code structure, an Indala FlexSecur compatible encoding, or another proprietary format your current readers expect. On the 13.56 MHz side, the card is built on genuine NXP silicon — genuine NXP MIFARE Classic 1K, genuine NXP MIFARE Plus, or genuine NXP DESFire EV3, depending on what your target smart reader platform requires. Both bands are encoded to match your specific system; neither is left as a generic blank.

The physical card substrate meets standard CR-80 dimensions (85.6 × 54 mm, 0.76 mm thick), is fully compatible with card printers and thermal-transfer overlaminates, and can be supplied as plain white PVC, pre-printed with artwork, or with a signature panel or magnetic stripe if secondary systems require it. The dual-antenna construction adds no measurable thickness compared to a standard single-technology card.

When You Need a Dual-Frequency Card

The most common driver is a phased migration from a legacy 125 kHz proximity infrastructure to a 13.56 MHz smart-card platform. Reader replacement across a large site — a corporate campus, a multi-building residential complex, or a university campus — is rarely completed in a single weekend. During the transition window, some doors carry new smart readers while others still run legacy prox hardware. Issuing two separate cards to every cardholder is operationally difficult and generates cardholder frustration. A single combi card removes that friction: the same credential works at every door regardless of reader generation.

Mixed-technology fleets are the second major use case. Some sites run 125 kHz readers at perimeter vehicle gates or car park barriers — where read range and weathering tolerance favour LF technology — while interior doors use 13.56 MHz smart readers for higher security or audit-logging capability. If your 125 kHz vs 13.56 MHz infrastructure splits along those lines, a dual-frequency card is the only single-credential solution. Sites with Gallagher Cardax proximity readers alongside newer smart platforms, or Vicon VAX compatible proximity hardware running in parallel with an upgraded 13.56 MHz access controller, are typical candidates.

Contractors, visitors and temporary workers accessing a site mid-migration represent a third scenario. Rather than managing two card pools — one for staff on full dual-generation access, one for legacy-only visitors — a combi card stock lets you issue a single credential type to all badge categories and simplify inventory management. The locksmith and integrator sector frequently procures dual-frequency cards as a standard line item precisely because projects rarely have a clean reader-cutover date.

Encoding Both Bands Correctly

Correct dual-frequency credential supply requires independent format matching on each band — the two are not related and must each be specified separately. On the 125 kHz band, you provide the same parameters you would for a single-technology prox card: format type (standard 26-bit, or a proprietary variant such as Lenel 42-bit, ADT 31-bit, Nedap proximity, or DMP custom format), facility code, and the card-number range. On the 13.56 MHz band, you specify the chip type and, for open-format platforms, the memory sector layout and any application identifier your reader firmware expects.

For 125 kHz formats where the proprietary encoding is not documented in open standards, we verify compatibility against a sample read from your existing reader infrastructure before encoding a production run. This is standard practice for multi-site migrations where a format error would cause a failed access event at every door. If you are unsure of your current 125 kHz format, the access card format identification guide outlines the steps to confirm encoding via an existing credential or reader configuration export.

On the 13.56 MHz band, open formats — MIFARE Classic sectors encoded to a known application structure, for example — are encoded to your application specification. Secured smart platforms such as HID Seos or MIFARE DESFire AES installations ship as compatible blank credentials ready for your own system's enrolment process; your access-control platform writes its own cryptographic keys during commissioning, exactly as it would with any other compatible blank. The MIFARE family guide covers the encoding and key-management distinctions across Classic, Plus, DESFire and Ultralight variants in detail.

Open and Secured Configurations on Each Band

The two frequency bands on a combi card can each be independently open or secured, and those two configurations need not match each other. A typical migration scenario pairs an open 125 kHz prox encoding — standard Wiegand, reader-verifiable with no cryptographic keys — with a secured 13.56 MHz smart-card configuration where the access controller holds the sector or application keys. This is intentional: the 125 kHz band maintains compatibility with legacy readers that have no key-management capability, while the 13.56 MHz band delivers the audit logging, anti-replay protection and sector-key security the new platform is intended to provide.

For sites targeting HID Seos on the smart band, or a similarly credential-centric platform, the 13.56 MHz blank ships without any factory keys loaded. Your HID access manager or equivalent controller enrols the card and writes the Seos application data during the standard credential-issuance workflow. The 125 kHz prox payload on the same card operates entirely independently and does not interact with the HID enrolment process. Both bands remain readable by their respective reader types after enrolment.

Where both bands are open — for instance, a site using standard 26-bit Wiegand on 125 kHz and MIFARE Classic with a known sector structure on 13.56 MHz — cards are supplied fully encoded and ready to issue without any further programming step. The 13.56 MHz HF smart cards and 125 kHz LF proximity cards catalogue pages describe the single-technology variants of each format; dual-frequency orders combine specifications from both.

Order Dual-Frequency Cards

To request a quote, provide the following for each band: the 125 kHz format type and any facility-code or card-number range constraints; the 13.56 MHz chip type and configuration (open encoded, secured blank, or secured with a specified open sector layout); total quantity required; and any substrate preferences. Contact our team with these details and we will confirm format compatibility, pricing and lead time within one business day. For first-time orders from a new site, sending a sample of your existing prox card allows us to verify the 125 kHz encoding before committing a production run.

Standard quantities start at 200 cards. Mixed-specification orders — for example, separate card-number ranges for staff and contractor pools, or multiple facility codes for a multi-site deployment — can be combined on a single purchase order. Bulk and wholesale procurement buyers working across multiple client sites can request tiered pricing at the quote stage. If your current setup involves replacing individual lost or damaged credentials rather than a full-batch reorder, note that dual-frequency blanks can be supplied in small quantities for single-card replacements with matching encoding.

Security ID Systems is an independent manufacturer and supplier of compatible access-control credentials and is not affiliated with, authorized by, or endorsed by HID Global, NXP Semiconductors, Gallagher, Lenel, ASSA ABLOY, or any other access-control system or chip manufacturer referenced on this page.