The C1 comlink was a small, cylindrical device with a mic grill on the top, an on/off switch fixed to the side and scrambler, transmitter and frequency code sequence controls inside the casing. The C1 could be tuned with sophisticated encryption algorithms to transmit and receive over secure frequencies, making it ideal for military applications. Within close range of an Imperial base, comlink signals were automatically boosted for optimum performance.
C1 comlinks were commonly used to supplement DH77 and DH107 helmet communication systems worn by Imperial stormtroopers. During his attempt to rescue Leia Organa onboard the first Death Star, Luke Skywalker kept in contact with C-3PO via a C1 comlink.