Door Monitoring & Alarms

Radiometrix code-hopping “K” products such as KTX2 and KRX2 can be used to implement an entry monitoring system.

Uses include private home alarm systems, site monitoring and asset management.

Real-life case study

A householder having Bed & Breakfast guests wanted to know if selected private areas of the house were being accessed. Locked doors were not an option since the private areas of concern were child bedrooms. Various burglar alarm systems were considered but none seemed to address the exact needs of the householder. A minimal impact and simple deployment were high priorities in this case.


  • Wireless system
  • 50 – 100m range
  • Two doors to be monitored (bedrooms)
  • Opening of a door activates a remote indicator and audible alarm
  • Closing the door has no effect
  • Comply with applicable legislation

Solution overview

For convenience in this particular example, two KFX2 (Keyfob) code-hopping transmitters were adapted for use with changeover reed switches (one per door). The KTX2 module is essentially the same as a KFX2 but without plastic case, buttons and batteries. A specific implementation could use KTX2 + battery + reed switch all in one small case.

The remote indicator and alarm device used a KDEC-44, which is KDEC software implemented on a slightly modified CTR44 demo board (This part is available as KDEC-44-000). Again, this was selected for convenience – a KDEC board could have been used or (if relay outputs were not required) a KRX2.

The KDEC software itself was also slightly modified to provide true latched outputs (rather than a toggle on/off). Up to four rooms could be monitored using a KDEC-44 board. To reset the outputs an external reset input was added: this was wired to a push-button. This variation in KDEC software (and others) is available on request when ordering your KDEC, or KRX2.