You are entering the most top-secret and secure room in the Bunker. Welcome to OSAX. Teletype operator Janet Puddicombe was one of the few allowed through these doors.

“…there were a lot of places in here that was restricted to a lot of people […] And you know, if you worked in OSAX, OSAX was the most restricted area. And that’s where I worked most of the time, was in there.”

The Bunker’s official name was Canadian Forces Station Carp. Between 1962 and 1995, the station was an active player in the global shift to computerized communications. The Ottawa Semi-Automatic Exchange—known as OSAX—was built into the Bunker in 1981 to replace a larger facility on the 400 level. OSAX was the hub of military communications, connecting the Bunker to a domestic and international network of receiver stations.

Once the doors were shut, the metal-clad room becomes what is known in the military as a “Faraday Cage”. That means it is totally secure from outside electronic surveillance—and can withstand the electromagnetic pulses emanating from a nuclear blast that would otherwise disable or destroy electronic devices. Entrance to this room was limited to those with top-secret clearance.

The two Burroughs B4800 computers, similar to those here, handled more than 100,000 messages a month. The large computers required a lot of ventilation and cabling; much of that is contained underneath the raised floor. The only connection to the outside world from this room is the secure fibre optic cable through the wall.