HUT Comms Lab., Timo O. Korhonen
An early exchange, call setup
nOne of the 100 subscribers lifts
his handset -> Call finder is activated to search the line.
nAfter
the line is located other relays connect the dial-tone generator.
nThe
subscriber selects two digits.
nThe
first digit selects the subscriber group by using the group
selector.
nThe
second digit selects the line selector.
nSelection
is done by sending pulses that move the selectors stepwise.
nWhen
connection is established a ringing tone is sent.
nNote
that only 10 subscribers of 100 can call at the same time to different
numbers! (why?) (concentration is 1:10)