GOSF Communications

The Facility featured two communications systems, both built on telephone technology.

Line A

The original network, "Line A", used 1940s technology and was purely analog. It was used heavily during the construction of the facility, and had under 1,000 numbers (3 digits long). A backup "Line B" with the same technology was also proposed, but never installed.

"Line A" was named as such because it originally started as just one line, to which an analog exchange was added later. It still featured a failsafe mode where if the exchange lost power, it would revert back to acting as one singular party line.

Cominet

The second network, known as "Cominet", was installed in the 1960s, during the later stages of the facility's construction. This network used digital telephone technology based on a specially commissioned version of Bell's T-Carrier system, and the intention was for it to provide data capabilities to new computer systems intended for the facility as well as expand the block of usable phone numbers to almost a million with 6-digit numbers.

After its activation, it was interconnected with the "Line A" network, which was mostly disused but still relied on as a backup and by various legacy systems (including the network of emergency call stations in the most remote areas of the facility).

Exchanges

Hundreds of telephone exchanges were built around the facility to cater to its various extents, though not every level had one - many of the Exertus floors would share a singular exchange. Some, in the furthest extents of the mapped cave systems, were simply left to rot when it had been decided they were no longer needed.

Due to the criticality of the telephone system in ensuring a safe evacuation, the exchanges had their own dedicated access routes and were exempt from the main cement vitrification system. To prevent contamination, they would be isolated from the main facility area by a series of concrete and steel bulkheads, ensuring they could be safely accessed during a disaster scenario even if the facility itself was unsafe.

Terminal Phones

Most Cominet devices including those located in apartments at Exertus were MULTEX terminal phones, consisting of a serial terminal connected to a phone handset and keyboard. Both the terminal and phone would share the same line, with a combined total bandwidth of 64kbps split into 62.67kbps for the handset and 1.33kbps for the terminal.