FSK (Frequency Shift Keying) Telemetry Module for Vector Measuring Current Meters

摘要

The EG&G Vector Measuring Current Meter (VMCM) used in mooring work provides a 20 ma Serial ASCII Instrumentation Loop (SAIL) communication system. A projected application of the VMCM is to have a surface mooring communicate with a series of VMCMs via a Frequency Shift Keying (FSK) link. While an FSK modem can communicate with the VMCM, a problem exists with the general operation of the VMCM. If the VMCM is addressed to dump data, it remains on until the unit is re-addressed. If a failure in the link occurs, then the VMCM stays on in a higher power mode and the batteries will be depleted early. The insertion of a processing block between the modem and the VMCM providers a way to look at incoming data, qualify it and re-transmit it to the VMCM. The VMCM will reply and the preprocessor can channel the data to the modem. In the event of a VMCM malfunction, the preprocessor has a timeout function and will turn off the carrier keeping the line quiet.