Subscriber Communicator (SC) is a wireless VHF modem that transmits messages from a user to the ORBCOMM System with delivery to an addressed recipient and receives messages from the ORBCOMM System intended for a specific user. 

Many manufactures have different proprietary designs and manufacturers are free to include unique features in their SC design. The SCs now have RS-232C ports for data uploading and downloading. Current options on a number of SCs include internal GPS receivers and/or additional digital and analog input and output ports. Stellar/Delphi and Quake are two manufacturers of ORBCOMM Subscriber Communicator.