Data Transmission Plan for Serving LASA, a Large Aperture Seismic Array in Montana

Common carrier telephone facilities-half-group restored polar data sets, open wire, and microwave radio-have been adapted to provide wideband data transmission service for M.I.T. Lincoln Laboratory's Montana LASA (large aperture seismic array). This paper describes the transmission plan and design objectives. Synchronous, 19.2 kilobit per second serial data are transmitted from each of 21 data gathering sites to LASA data center (LDC) at Billings, Montana. From LDC, 19.2 kilobit per second timing and 1.2 kilobit per second control data are sent toward each site. A voice coordinating channel has been provided between LDC and each site. In order to meet the service date, these channels were multiplexed on the single open wire pair connecting each site with a specified microwave radio station by use of directional and cut-apart filters, and vestigial sideband demodulators not specifically tailored to this application. Despite resulting signal constraint toward the sites, modified but valuable remote test features that are available on the wideband data station are preserved. The service requirements of widely scattered array have been met, and performance has been satisfactory through all environmental conditions thus far experienced.