The following information obtained from UNAVCO's online DOI system:
(https://www.unavco.org/data/doi/search/search.html)

SCIGN USGS GPS Network - SGLG-Signal Mtn. GPS P.S.
Start: 05-Feb-2015
End: 05-Dec-2019
Hudnut, Kenneth, Determan, Daniel N., Aspiotes, Aris G., 2015, SCIGN USGS GPS Network - SGLG-Signal Mtn. GPS P.S., UNAVCO, GPS/GNSS Observations Dataset, 
https://doi.org/10.7283/T53X84XV