HUT Comms Lab., Timo O. Korhonen
PSTN exchange development
nRegister-controlled
setup (1920 -)
nB-subscriber
number receiver by a register
nregister
controls all the remaining call setup stages
nDistributed
control
nMarkers
indicate idle switches
nThus
markers control path routing
nStored
program control, 1960s and 1970s (SPC)
nNew
services
nsupervision
(operation & maintenance O&M)
nintegrated
charging
ngathering
statistics
nIN
services
nEasier
updating and maintenance
