code ringing การใช้

When calling a party, the operator used code ringing, a distinctive ringing signal sequence, such as two long rings followed by one short ring.
The two subscribers on a two-party line would have separate three-letter then four digit numbers in a special number group, and had selective ringing to the party required only ( code ringing with a letter suffix for the code required was not used ).
In the Bell System, the two stations were thus called the " tip party " and the " ring party ", In combination with code ringing, this method could be extended to four and eight subscribers to reduce the number of disturbances.