Description
ALARM.COM | ADC-AC-ET20 Single-Gang Multi-Technology Access Control Reader
Proximity, MIFARE DESFire, NFC and Bluetooth Low Energy credential support with Wiegand, OSDP Secure Channel and patented OSDP Auto-Detect.
One Reader for Cards, Fobs and Mobile Credentials
The Alarm.com ADC-AC-ET20 Single-Gang Reader combines multiple credential technologies in one modern access control reader. It supports legacy 125 kHz proximity credentials, compatible MIFARE DESFire smart credentials, NFC and Bluetooth Low Energy, allowing organizations to support existing cards and fobs while transitioning to encrypted smart credentials and mobile access.
Alarm.com Mobile Credentials allow authorized users to unlock doors with a compatible smartphone, reducing reliance on physical badges. This provides a convenient credential option for employees while helping administrators streamline credential distribution and eliminate many of the costs associated with replacing lost or forgotten access cards.
Designed for installation over a standard single-gang electrical box, the ADC-AC-ET20 offers a professional appearance for offices, retail stores, schools, healthcare facilities, multifamily properties and other commercial access control applications. Support for both Wiegand and OSDP makes the reader suitable for new installations and compatible retrofit projects.
Multiple Credential Technologies in a Single Reader
The ADC-AC-ET20 provides a flexible migration path from legacy proximity badges to more secure smart and mobile credentials. Businesses can maintain support for compatible existing credentials while introducing MIFARE DESFire, NFC and Bluetooth Low Energy access options according to their security and operational requirements.
Key Features
- Single-gang access control reader
- Legacy 125 kHz proximity credential support
- MIFARE DESFire EV1, EV2 and EV3 reading capability
- NFC credential technology
- Bluetooth Low Energy mobile credential support
- Phones can unlock doors with Alarm.com Mobile Credentials
- Wiegand and OSDP communication
- OSDP Secure Channel enabled
- Patented OSDP Auto-Detect functionality
- Automatic transition from Wiegand to OSDP
- Visual LED and audible credential feedback
- Accelerometer-based tamper detection
- IP55-rated enclosure
- Compatible with Alarm.com access control solutions
Common Applications
- Commercial office entrances
- Small and midsize businesses
- Retail stores and restricted stockrooms
- Multifamily residential properties
- Apartment offices and amenity areas
- Healthcare and medical offices
- Schools and educational facilities
- Warehouses and industrial buildings
- Employee-only entrances
- Server rooms and sensitive areas
- Interior and exterior access points
- Mobile-first access control deployments
- Legacy proximity credential migrations
- Wiegand-to-OSDP upgrade projects
Unlock Doors with Alarm.com Mobile Credentials
Bluetooth Low Energy support enables the ADC-AC-ET20 to communicate with compatible smartphones using Alarm.com Mobile Credentials. Once an authorized mobile credential is issued and properly configured, the user’s phone can serve as the access credential—eliminating the need to present a traditional badge at the reader.
- Provides a convenient alternative to physical badges
- Reduces costs associated with lost or replacement cards
- Allows credentials to be issued and revoked electronically
- Supports mobile-first and mixed-credential environments
- Helps organizations transition gradually from legacy proximity cards
Mobile credential operation requires compatible Alarm.com access control hardware, an eligible Alarm.com service plan, the applicable mobile application and configuration through an authorized Alarm.com service provider.
OSDP Auto-Detect and Secure Channel
The ADC-AC-ET20 is fully OSDP compliant and supports OSDP Secure Channel for encrypted communication between the reader and a compatible access control panel. OSDP provides bidirectional reader communication, enhanced supervision and stronger protection than traditional unencrypted Wiegand communication.
Alarm.com’s patented OSDP Auto-Detect allows the reader to communicate using Wiegand and OSDP over the same data wires. When the reader detects a compatible OSDP message during startup, it can automatically transition to OSDP communication without requiring the installer to replace the existing reader wiring. Operation can vary by reader firmware, so the current Alarm.com installation instructions should be followed during setup.
ADC-AC-ET20 Technical Specifications
| Manufacturer | Alarm.com |
| Model | ADC-AC-ET20 |
| Form Factor | Single-Gang Reader |
| RF Technologies | 125 kHz, 13.56 MHz, NFC and BLE |
| Communication | Wiegand and OSDP |
| Input Power | 5–16 VDC |
| Maximum Current | 169 mA |
| Ingress Protection | IP55 |
| Dimensions | 5.1 × 3.3 × 0.7 in. |
| Operating Temperature | -31°F to 151°F |
Important Credential Compatibility Information
Although the ADC-AC-ET20 supports several MIFARE DESFire technologies, this does not mean that every independently programmed MIFARE or DESFire credential will operate with the reader and Alarm.com access control system.
Alarm.com identifies its DESFire EV2 smart credential support as compatible with Alarm.com and WaveLynx-branded EV2 smart credentials. Confirm credential brand, technology, programming, bit format and Alarm.com system compatibility before ordering replacement cards or fobs.
Single-Gang Installation and Wiring
The reader is designed to mount over a standard single-gang box using the included wall plate. It can also be surface mounted with appropriate anchors and hardware for the mounting surface.
- Recommended reader cable: 22/6 stranded shielded wire
- Maximum Wiegand distance varies by wire gauge
- OSDP supports up to 1,000 feet at 9600 baud using specified 22 AWG twisted-pair wiring
- OSDP is recommended for secure, supervised reader communication
- Reader firmware determines the applicable Auto-Detect and reset procedure
- All wiring must comply with applicable electrical and life-safety requirements
Why Choose the Alarm.com ADC-AC-ET20?
The ADC-AC-ET20 provides a practical combination of legacy credential support and modern access technology in one clean single-gang reader. Proximity compatibility helps preserve existing credential investments, while MIFARE DESFire, NFC and Bluetooth Low Energy support create a path toward encrypted smart cards and phone-based door access. OSDP Secure Channel and OSDP Auto-Detect further strengthen the reader’s value for secure new installations and Wiegand-to-OSDP modernization projects.
ADC-AC-ET20 Frequently Asked Questions
What credentials does the ADC-AC-ET20 read?
The reader supports compatible 125 kHz proximity credentials, MIFARE DESFire EV1, EV2 and EV3 technologies, NFC and Bluetooth Low Energy mobile credentials. Exact credential compatibility must be verified before ordering.
Can a smartphone unlock a door using the ET20?
Yes. The ET20 supports Alarm.com Mobile Credentials through Bluetooth Low Energy. A compatible Alarm.com account, service package, mobile application and professional configuration are required.
What is OSDP Auto-Detect?
OSDP Auto-Detect allows the reader to listen for compatible OSDP communication during startup and automatically transition from Wiegand to OSDP operation without replacing the existing data wires.
Does the ET20 support OSDP Secure Channel?
Yes. The ADC-AC-ET20 is OSDP compliant and supports Secure Channel when connected to compatible, properly configured access control hardware.
Will every MIFARE DESFire card work with this reader?
No. Alarm.com specifically identifies Alarm.com and WaveLynx-branded EV2 smart credentials as compatible. DESFire technology alone does not guarantee system compatibility.
Is professional installation required?
Yes. Alarm.com access control products are intended for professional installation and configuration through an authorized Alarm.com service provider.
Alarm.com ADC-AC-ET20 Resources
Review the official Alarm.com documentation for credential compatibility, wiring, OSDP configuration, firmware-specific instructions and installation requirements.
Access Control Readers Data Sheet ET20 Installation Guide PDF
