Nyquist C4000 Series System Software - Intercom Call License. ntercom calling is disabled by default on every C4000 system. Installing this license enables intercom calling (i.e., talkback operation) between any two applicable Nyquist devices (VoIP phones, VoIP speakers, VoIP Intercom Modules, Web UI dashboard, etc.). Each NQ-C4000ICL license key installed/added to a system incrementally increases the concurrent Intercom Call limit by 1. For example, installing three (3) NQ-C4000ICL licenses will permit up to 3 concurrent intercom calls on a system. Note: The Intercom Call limit can never exceed the system’s maximum Concurrent Call limit (ref. the NQ-C4000CCLX license description above).