This code system http://hl7.org/fhir/deviceassociation-operationstatus defines the following codes:

CodeDisplayDefinition
on OnThe device is working or switched on, i.e. active.
off OffThe device is inactive, switched off, or deactivated.
standby Stand ByThe device is in stand-by mode i.e. not actively working but not powered off.
defective Stand ByThe device is defective or for maintenance and is not available or working.
unknown UnknownThe operational status of the device has not been determined.
<status value="active"/><experimental value="false"/><date value="2021-01-05T10:01:24+11:00"/><publisher value="HL7 (FHIR Project)"/><contact><telecom><system value="url"/><value value="http://hl7.org/fhir"/></telecom><telecom><system value="email"/><value value="fhir@lists.hl7.org"/></telecom></contact><description value="The operational status of the device."/><jurisdiction><coding><system value="http://unstats.un.org/unsd/methods/m49/m49.htm"/><code value="001"/><display value="World"/></coding></jurisdiction><caseSensitive value="true"/><valueSet value="http://hl7.org/fhir/ValueSet/deviceassociation-operationstatus"/><content value="complete"/><concept><code value="on"/><display value="On"/><definition value="The device is working or switched on, i.e. active."/></concept><concept><code value="off"/><display value="Off"/><definition value="The device is inactive, switched off, or deactivated."/></concept><concept><code value="standby"/><display value="Stand By"/><definition value="The device is in stand-by mode i.e. not actively working but not powered off."/></concept><concept><code value="defective"/><display value="Stand By"/><definition value="The device is defective or for maintenance and is not available or working."/></concept><concept><code value="unknown"/><display value="Unknown"/><definition value="The operational status of the device has not been determined."/></concept></CodeSystem>