The Digital Radiation Monitor 
(discontinued), can be used the TI-Nspire Lab Cradle 
, but only if the correct cable is used. Until June 2011, Digital Radiation Monitors were shipped with a cable that will not work with the the Lab Cradle. Updated cables can be identified by a 2mm red shrink wrap band on the monitor end of the cable (see image).
If you have an older cable without the shrink wrap, let us know and we will replace the cable for you.
Cable for Digital Radiation Monitor (RCD-BTD)