coded ringing造句

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.
It's difficult to find coded ringing in a sentence. 用coded ringing造句挺难的