Ship To Ship Pulse Recognition System
E. H. Krause, M. W. Rosen Jr · 1941
A completely automatic ship to ship recognition system utilizing ultra-high frequencies is described. A very short signal (on the order of a millisecond long) consisting of a group of pulses, constitute the challenging and replying signals. A total of 4100 different codings is provided with the reply coded independently of the challenge. An optical reply system is included to corroborate or replace the radio reply at the will of the challenging operator. The automatic operation as well as the coding is obtained almost completely through the use of electronic circuits employing vacuum tube switches and counters. The results of tests conducted on the complete system over a land distance of eight miles are discussed.