Linear ACT-21B 1-channel block coded key ring transmitter

The Model ACT-21B 1-Channel Block Coded Key Ring Transmitter is designed for use with Linear’s access control products. The Model ACT-21B is a single-channel device supplied with a quick-disconnect key ring. Also included are lithium batteries with a five-year service life. A unique 10-second time-out feature prevents the system from being shut down by a single transmitter transmitting continuously.

The transmitter is MegaCode format, which means each transmitter is factory preprogrammed with one of over 1,000,000 codes, virtually eliminating the possibility of code duplication. Because the receiver ”learns” each specific code, no unauthorized person can gain access to the system by reprogramming a transmitter.

Block coded transmitters are factory programmed to a sequential series of transmitter ID codes. When used with a Linear access controller, transmitters can be locally or remotely programmed into memory by entering the first and last codes of the block into the system. Facility codes can be selected to further customize the system.

Order number: ACP00615



  • Compatible with all Linear access receivers and controllers
  • Supplied with quick-disconnect key ring
  • Sold in lots of 10
  • Power: Two 1616 batteries
  • Codes: Custom block coded in MegaCode format

General specifications

  • Frequency: 318 MHz
  • Number of Codes: 1,000,000 plus
  • Block Coding: Units are sequentially coded at the factory to customers specifications. Facility code may be specified.
  • Channels: one channel
  • Power: two 3V 1616 style batteries (supplied)
  • Battery Life: up to three years
  • Dimensions: 1.25" W x 2.25" H x .48" D (32 x 57 x 12 mm)
Compatible models

Models compatible with the ACT-21B

  • AE1000Plus : Commercial Telephone Entry System with Access Control - Four Doors
  • AE2000Plus : Commercial Telephone Entry System with Access Control - Four Doors, Large Screen
  • AKR-1 : Exterior Digital Keypad with Radio Receiver
  • AM-RPR : Remote Proximity Receiver
  • AM-RRR : Remote Radio Receiver
  • AM3Plus : 4-Portal Access Controller
  • MDR : 1-Channel Receiver
  • MDR-2 : 2-Channel Receiver
  • MDRG : 1-Channel Gate Receiver
  • SMDRG : 1-Channel Gate Receiver
  • WOR : Wiegand Output Receiver
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