olemus
kärgvõrgu marsruutimiskeskus, tavalise telefonijaama analoog
=
a central point to which base stations of cells in a cluster are connected to, the mobile equivalent of a PSTN central office

piltlikult
https://www.city.ac.uk/__data/assets/image/0006/296547/monile-switching-office.jpg

ülevaateid
http://www.tech-faq.com/mtso-mobile-telephone-switching-office.html

https://en.wikipedia.org/wiki/Mobile_Telephone_Switching_Office