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The technical aspects, are using SVR "sites" locations signals, this is the russian equipmment
This is NATO machine for surveillance -
HP 831065-S01 Smart Buy Ml30 Gen9 E3-1230V5 4G Us Svr
https://www.newegg.com/Product/Product.aspx?Item=2NS-0006-0JN60
This is how the secret service, here at Portugal, use the national hidden video surveillance, trought the SVR signals of the train network