Apartment, Multifamily & Rental Property Access Control
Apartment building access control hardware: anti-clone readers with matched fob sets, QR visitor codes, 4G controllers for rentals and UHF tags for gates.
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LF-120 125 kHz EM4100 Reader Module with TTL, Wiegand 26 or RS232
40 × 40 mm board-level reader for EM4100/TK4100 cards, ordered with TTL UART, Wiegand 26 or RS232 output, plus card-present and buzzer/LED drive pins.
- Reads 125 kHz EM4100, TK4100 and compatible cards and fobs at more than 50 mm
- Three output versions: TTL UART, Wiegand 26 or RS232
- TTL version: continuous or single card-number output, selected on pin A0
- Card-present status on A1 and a 200 ms buzzer/LED drive pulse on A2
- Serial speed configurable by command, 9600–115200 bit/s (default 115200)
- Frequency
- 125 kHz (EM4100/TK4100)
- Output
- TTL / Wiegand 26 / RS232 (by version)
- Read range
- > 50 mm
- Power
- 5 V DC ±5%, < 100 mA
- Dimensions
- 40 × 40 mm (±3 mm)
- Operating temperature
- –10 to +70 °C
Reply within 24 hours Tested before dispatch Worldwide shipping
125 kHz EM4100 Reader Module with TTL, Wiegand 26 or RS232: overview
The LF-120 is a 125 kHz EM4100 reader module for device makers who want a ready low-frequency front end instead of designing their own RF circuit. It reads EM4100, TK4100 and compatible cards and key fobs at more than 50 mm and is ordered in one of three output versions: TTL serial, Wiegand 26 or RS232. The 40 × 40 mm board suits lockers, vending machines, attendance terminals and access panels that have space for a square module.
On the TTL version, pin A0 decides whether the card number is sent once per presentation or repeated for as long as the card stays in the field, which helps lockers and kiosks that need to know a card is still there. The Wiegand 26 and RS232 versions send the number once per read. Serial speed is set by command anywhere from 9600 to 115200 bit/s, with 115200 as the default.
Two status pins cut down host firmware work. A1 reports whether a card is present (logic 0) or absent (logic 1), and A2 goes high for 200 ms on every read so it can trigger a buzzer and LED.
Integration notes
All signals come out on a 12-position, 2.54 mm pitch header (P1). The antenna coil connects either to header pins ANT1/ANT2 or to an optional 2.0 mm horizontal socket (J1). Supply is 5 V DC (±5%) with current below 100 mA, and the module operates from –10 to +70 °C. A smaller 32.5 × 17.5 mm board with the same pin assignment is available as the LF-130.
More features
- 40 × 40 mm board, 2.54 mm pitch pins; coil via header pins or optional 2.0 mm socket
- 5 V DC (±5%), under 100 mA; operates from –10 to +70 °C
LF-120 specifications
RF & credentials
| Frequency | 125 kHz |
|---|---|
| Credentials | EM4100, TK4100 and compatible cards/fobs |
| Read distance | > 50 mm (depends on card type and installation environment) |
Interfaces
| Output | TTL UART, Wiegand 26 or RS232 (one per version) |
|---|---|
| Serial baud rate | 9600–115200 bit/s, set by command (default 115200) |
| Output mode | TTL: continuous or once per card (pin A0); Wiegand 26 and RS232: once per card |
| Status lines | Card present (A1); buzzer/LED drive, 200 ms high on read (A2) |
Electrical
| Supply voltage | 5 V DC (±5%) |
|---|---|
| Operating current | < 100 mA |
Mechanical & environment
| Module connection | 2.54 mm pitch pins |
|---|---|
| Antenna connection | 2.54 mm header pins (ANT1/ANT2) or optional 2.0 mm horizontal socket |
| Dimensions | 40 × 40 mm (±3 mm) |
| Operating temperature | –10 to +70 °C |
| Storage temperature | –20 to +80 °C |
| Operating humidity | 15–90% RH |
Output versions
| Variant SKU | Supply | Interface | Card-number output |
|---|---|---|---|
| LF-120-E-T | 5 V DC | TTL UART | Continuous or once per card (set on pin A0) |
| LF-120-E-W | 5 V DC | Wiegand 26 | Once per card read |
| LF-120-E-RS232 | 5 V DC | RS232 | Once per card read |
Pin definition
| Pin | Signal | Function |
|---|---|---|
| P1-1 | VCC | Power supply + |
| P1-2 | GND | Ground |
| P1-3 | TXD/WG0 | Serial TXD (TTL/serial versions) or Wiegand DATA0 |
| P1-4 | WG1 | Wiegand DATA1 |
| P1-5 | NC | Not connected |
| P1-6 | NC | Not connected |
| P1-7 | NC | Not connected |
| P1-8 | ANT1 | Antenna coil terminal 1 |
| P1-9 | ANT2 | Antenna coil terminal 2 |
| P1-10 | A0 | Output mode: 0 = repeat serial output while card present, 1 = output once (UART only; Wiegand always once) |
| P1-11 | A1 | Card status: 0 = card present, 1 = no card |
| P1-12 | A2 | Buzzer/LED drive: 200 ms high level on each card read |
| J1-1 | TX1 | Optional 2.0 mm horizontal antenna socket, contact 1 |
| J1-2 | TX2 | Optional 2.0 mm horizontal antenna socket, contact 2 |
P1: 12-position header, 2.54 mm pitch. J1: optional 2.0 mm horizontal antenna socket.
Specifications can change between production batches. Confirm the current revision with us before placing volume orders.
Ordering options
Quote the SKU that matches your frequency, interface and mounting. Not sure? Send us your controller model and we will pick the variant for you.
| SKU | Configuration | Actions |
|---|---|---|
| LF-120-E-T | 125 kHz EM4100 module, 40 × 40 mm, TTL UART output (continuous or single mode) | |
| LF-120-E-W | 125 kHz EM4100 module, 40 × 40 mm, Wiegand 26 output | |
| LF-120-E-RS232 | 125 kHz EM4100 module, 40 × 40 mm, RS232 output |
Where the LF-120 is used
- Locker and cabinet controllers that watch the TTL version for continued card presence
- Time-attendance terminals reading the RS232 version on a serial port
- Door and gate panels that need a Wiegand 26 reader running from a 5 V rail
- Vending and self-service machines that identify members by EM4100 fob
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LF-120 FAQ
What is the difference between the three LF-120 versions?
They share the same card support, read range, pinout and electrical ratings; only the output differs. LF-120-E-T sends TTL serial data, LF-120-E-W outputs Wiegand 26 and LF-120-E-RS232 sends RS232 serial data.
Can the module keep reporting a card that stays on the reader?
Yes, on the TTL version. With A0 at logic 0 the card number repeats while the card remains in the field; at logic 1 it is sent once. Wiegand output is always sent once per read.
How far does it read?
More than 50 mm, depending on the credential and the installation. Metal close to the coil shortens range, so test in your final enclosure.
Which baud rates are supported?
Serial speed is configurable by command from 9600 to 115200 bit/s. The default setting is 115200 bit/s.
How is the antenna coil connected?
Solder the coil to header pins ANT1 and ANT2 (P1-8, P1-9), or order the optional 2.0 mm horizontal socket (J1) for a plug-in coil.
Before you buy
Related buyer guides
Wiegand vs OSDP vs RS485: Which Reader Interface Should You Specify?
Compare Wiegand, OSDP and RS485 reader interfaces: wiring, cable limits, AES-128 Secure Channel and steps for a compatible access-control migration.
125kHz vs 13.56MHz: Choosing Access Cards and Readers
125 kHz cards are cheap but easy to clone; 13.56 MHz cards add memory and, on DESFire-class chips, AES security. Compare range, chips, security and migration.
Wiegand 26-Bit Format Explained (with a Free Calculator)
Wiegand 26-bit is an even parity bit, 8-bit facility code, 16-bit card number and odd parity bit. Convert card numbers to hex and back with the calculator.
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Get pricing for the LF-120
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