PDP-11/24, with the provision for user installable I/O cards including asynchronous and synchronous modules. This product was used as one of the earliest commercial platforms upon which networking products could be built, including X.25 gateways, SNA gateways, routers, and terminal servers. Ethernet adaptors, such as the DEQNA Q-Bus card, were also available. Many of the earliest systems on the ARPANET were PDP-11's Peripherals A wide range of peripherals were available; some of them were also used in other DEC systems like the PDP-8 or PDP-10. The following are some of the more common PDP-11 peripherals. CR11 – punched card reader DL11 – single serial line for either RS-232 or current loop LA30/LA36 – DECwriter dot-matrix printing keyboard terminal LP11 – high speed line printer PC11 – high speed papertape reader/punch RA, RD series – fixed platter hard disk RK series – hard disk with exchangeable platter RL01/RL02 – hard disk with exchangeable platter RM, RP series – exchangeable multi-platter hard disk RX01/RX02 – 8-inch floppy disk RX50/RX33 – 5.25 floppy disk TU10 – 9 track tape drive TU56 – DECtape block-addressed tape system VT05/VT50/VT52/VT100/VT220 – video display terminal Use The PDP-11 family of computers was used for many purposes. It was used as a standard minicomputer for general-purpose computing, such as timesharing, scientific, educational, medical, government or business computing. Another common application was real-time process control and factory automation. Some OEM models were also frequently used as embedded systems to control complex systems like traffic-light systems, medical systems, numerical controlled machining, or for network-management. An example of such use of PDP-11s was the management of the packet switched network Datanet 1. In the 1980s, the UK's air traffic control radar processing was conducted on a PDP 11/34 system known as PRDS – Processed Radar Display System at RAF West Drayton. The software for the Therac-25 medical linear particle accelerator also ran on a 32K PDP 11/23. In 2013, it was reported that PDP-11 programmers would be needed to control nuclear power plants through 2050. Another use was for storage of test programs for Teradyne ATE equipment, in a system known as the TSD (Test System Director). As such, they were in use until their software was rendered inoperable by the Year 2000 problem. The US Navy used a PDP-11/34 to control its Multi-station Spatial Disorientation Device, a simulator used in pilot training, until 2007, when it was replaced by a