An FSK telemetry module for vector measuring current meters

Abstract

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 the VMCM provides a way to look at incoming data. qualify it re-transmit it to the VMCM. The VMCM will reply and preprocessor can channel the data to the modem. In the event VMCM malfunction. the preprocessor has a timeout function will turn off the carrier keeping the line quiet.