olemus
kommutatsiooniväli kaablite ühendamiseks telefonijaamas
= a signal distribution frame or cable rack used in telephony to interconnect and manage telecommunication wiring

näiteid
https://c8.alamy.com/comp/A30R01/main-distribution-frame-A30R01.jpg

http://www.columbia.edu/cu/computinghistory/ocs1.jpg

https://i.pinimg.com/originals/f5/4d/ee/f54dee8179150c14cbc8d229297421bc.jpg

https://duckduckgo.com/?q=main+distribution+frame&t=h_&iar=images&iax=images&ia=images

ülevaateid
https://en.wikipedia.org/wiki/Main_distribution_frame