ards or positions may
complete the connection herself between any two lines terminating at
her own board. If, however, the line called for terminates at another
one of the boards, the operator makes use of the transfer or trunk line
extending to that board, and the operator at this latter board
completes the connection, so that the two subscribers' lines are
connected through the trunk or transfer line. A distinguishing feature,
therefore, in the operation of so-called transfer switchboards, is that
an operator can not always complete a connection herself, the
connection frequently requiring the attention of two operators.

Transfer systems are not now largely used, the multiple switchboard
having almost entirely supplanted them in manual exchanges of such size
as to be beyond the limitation of the simple switchboard. At
multi-office manual exchanges, however, where there are a number of
multiple switchboards employed at various central offices, the same
sort of a requirement exists as that which was met by the provision of
trunk lines between the various simple switchboards in a transfer
system. Obviously, the lines in one central office must be connected to
those of another in order to give universal service in the community in
which the exchange operates. For this purpose inter-office trunk lines
are used, the arrangement being such that when an operator at one
office receives a call for a subscriber in another office, she will
proceed to connect the calling subscriber's line, not directly with the
line of the called subscriber because that particular line is not
within her reach, but rather with a trunk line leading to the office in
which the called-for subscriber's line terminates; having done this she
will then inform an operator at that second office of the connection
desired, usually by means of a so-called order-wire circuit. The
connection between the trunk line so used and the line of the
called-for subscriber will then be completed by the connecting link or
trunk line extending between the two offices.

In such cases the multiple switchboard at each office is divided into
two portions, termed respectively the _A_ board and the _B_ board.
Each of these boards, with the exception that will be pointed out in a
subsequent chapter, is provided with a full complement of multiple
jacks for all of the lines entering that office. At the _A_ board are
located operators, called _A_ operators, who answer all the calls