tone, signalling them to press the restart button so that the unit could then start up for "new day" or otherwise known as "HJ's" by the radiomen. This took place after the new day's crypto keylist card was properly inserted into the "crib" or the card reader by securing it onto pins and then firmly closing the card access door and then locking it with a key. Once the unit(s) were restarted, the key was placed back in the safe using two-person integrity (TPI) which was stringently enforced following the Walker spy investigation. In the early nineties when the KWR-37 units were retired from the navy and replaced by the more reliable and modern KWR-46's, fleet Radiomen breathed a sigh of relief because the KWR-37 units were often unreliable and would occasionally fall out of synchronization timing, resulting in a loss of broadcast messages from the various fleet channels. Sources The KWR-37 On-line Crypto Receiver — Jerry Proc: "Crypto Machines", HMCS Haida National Historic Site (2010). Experiences operating the KWR-37 - a personal account from a retired US Navy fleet Radioman National Security Agency encryption devices