EM4100 (64-bit Read-Only) Compatible Cards & Fobs
The world's baseline 125 kHz credential: EM4100's 64-bit read-only ID, transmitted in Manchester-encoded ASK, is what most simple prox systems, time clocks, and gym doors actually run on.
Does American Key Cards make EM4100 (64-bit Read-Only) compatible cards?
Yes — American Key Cards supplies unbranded EM4100 (64-bit Read-Only) compatible cards and key fobs (AKC EM4100-Compatible Clamshell Card), encoded to your facility code and card-number range and ready to use on your existing EM Microelectronic readers. No hardware changes and no dealer account required.
- 125 kHz
- Frequency
- RFID prox
- Technology
- 1
- Bit format
- 3+
- OEM part nos.
- American Key Cards
- Order from
Before proximity access got complicated, it was EM4100 — a tiny read-only chip holding a factory-programmed 64-bit number that a reader picks up and passes along. It became the global default for everything that needed a cheap, reliable tap: time clocks, gym turnstiles, parking gates, apartment doors, asset tags. There's no facility-code-and-card-number structure to manage in the classic sense; each chip simply carries its ID, and the system's software decides what that ID is allowed to do. That simplicity is why EM4100 stock never really goes obsolete and why compatible supply is straightforward. We manufacture unbranded EM4100-compatible cards and key tags — including the widely interchangeable TK4100 and H4100 IC variants — programmed to the IDs your system expects and verified before shipping, so they read on your EM readers the moment they arrive.
EM4100 (64-bit Read-Only) specifications
- System brand
- EM Microelectronic-Marin SA
- Technology
- Passive RFID proximity
- Frequency
- 125 kHz
- Credential platform
- EM4100 read-only IC: 64-bit factory-programmed ROM, ASK modulation, Manchester encoding, on-chip resonance and rectification
- Bit formats
- 64-bit EM4100 protocol: 9 header bits + 40 data bits + 14 parity bits + 1 stop bit, Manchester-encoded ASK
- OEM part numbers
- EM4100, TK4100 (compatible IC), H4100 (compatible IC)
Specifications reviewed August 2026
Our compatible EM4100 (64-bit Read-Only) credentials
American Key Cards manufactures unbranded credentials engineered to work with your existing EM Microelectronic readers — no hardware changes, encoded to your facility code and card-number range before they ship.
Full specifications, form factors and ordering FAQ: Standard 125 kHz proximity cards
American Key Cards is an independent manufacturer of unbranded, compatible-by-specification credentials. We are not affiliated with, endorsed by, or sponsored by EM Microelectronic, and we never supply OEM-branded product — for brand-original credentials, order from EM Microelectronic or an authorized dealer. Brand names appear only to identify compatibility, and all trademarks remain the property of their respective owners.
Where EM4100 (64-bit Read-Only) is used
- Basic door access on EM-reader systems
- Time-and-attendance tracking
- Parking and vehicle gate access
- Gym and recreational facility entry
- Low-cost asset identification
Works with these readers
Related formats
You might also need
EM4102 (64-bit Read-Only Variant)
EM4100's identical twin: EM4102 transmits the same 64-bit read-only protocol, so the two are interchangeable on any EM-protocol reader — a detail worth knowing so you don't overthink a reorder.
View compatible cardsEM4200 (128-bit Enhanced Read-Only)
EM4100 with more room and more reach: EM4200 offers up to 128 bits and better read range while staying backward-compatible with EM4100 readers in 64-bit mode — plus an ISO animal-ID mode for tagging.
View compatible cardsHID Prox H10301 (Standard 26-Bit)
The most widely deployed proximity format in North America: 26-bit Wiegand — an 8-bit facility code plus 16-bit card number — on the 125 kHz HID Prox platform, live on millions of doors.
View compatible cardsEM4100 (64-bit Read-Only) — FAQ
What is the EM4100 chip and how does it work?
A passive 125 kHz read-only transponder carrying a 64-bit factory-programmed ID. Powered by the reader's field, it transmits its number in Manchester-encoded ASK; the reader hands that number to your system, which decides access. There's no battery and no writable data.
Are your EM4100 cards compatible with TK4100 readers?
Yes — TK4100 and H4100 are protocol-compatible ICs that read on the same EM4100 infrastructure. We supply whichever your system expects; functionally they're interchangeable on EM-protocol readers.
How is an EM4100 credential identified for reordering?
Your access software lists the enrolled IDs, and many EM cards have the number laser-printed on the surface. Send us the ID list or photos of working cards, and we program compatible stock to match — or supply fresh sequential IDs if you're expanding.
Can compatible EM4100 stock mix with our existing cards?
Yes — the reader only cares about the 64-bit ID, so compatible and original EM4100 credentials coexist on the same system. We coordinate IDs with your existing enrollment so there are no conflicts.