Voice band modems continue to be used worldwide for commercial, industrial, and military applications. Use cases include Secure telephone calls (STE, STU phones), Out of Band remote access, Point of Sale payment processing, Utility Metering, Environmental monitoring, and many other remote data applications. Throughout the course of lawful interception and infrastructure monitoring activities, extraction of the data contained within these voice band communications is often pertinent.

voice dataVOCAL’s voice band data demodulation software provides that data extraction functionality for V.21, V.22, and V.32 modem communications. VOCAL’s voice band data demodulation software operates on audio captures that can be taken either within the telecommunication network, PSTN central office, or one of the modem endpoints. The modem negotiation and training processes are examined by VOCAL’s data demodulation software to automatically determine communications standards and modulation parameters. The demodulated bit stream is passed through synchronous or asynchronous link layer protocols including HDLC, and SDLC, and V.14 to extract the byte-oriented data stream. Link layer protocols include CRC and parity verification where applicable. When high-speed full duplex modulations are used, echo cancellation is considered to improve demodulation performance.




Modem Modulations


Data Protocols


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