This is the CodeSystem that contains all the codes in CommunicationCategory (http://terminology.hl7.org/CodeSystem/communication-category) and CommunicationCategory (http://terminology.hl7.org/CodeSystem/communication-category). E.g. what you have to deal with if you get resources containing codes in either of them
Generated Narrative: CodeSystem 2c77c26f-0eba-4543-89eb-09eda3cba01c-740
This code system http://hl7.org/fhir/comparison/CodeSystem/2c77c26f-0eba-4543-89eb-09eda3cba01c-740
defines codes, but no codes are represented here