usy-test relay
is connected to the guard wire or busy-test wire of the called line, and
if that line be busy, the relay interferes with the control exercised by
the rotary switch upon the signal-transmitter controller, and the
controller is prevented from taking the step required to connect the
line. Thus, when a busy line is encountered, the final step of the
rotary switch is taken to set up the conversation conditions, but the
signal-transmitter controller does not take its final step; by this
failure of the signal-transmitter controller due to the action of the
busy-test relay, the calling line is not connected to the called line
but is connected to a busy-back tone generator instead.

Whether the line encountered be busy or idle, the connective division
remains in its condition as then adjusted until the subscriber hangs his
receiver upon the hook switch to obtain disconnection. The ringing of
the bell of the called station is done directly by the calling
subscriber in pressing the ringing key.

The disconnection is effected, when the receiver of the calling line is
hung up, by the supervisory relay in the central office, whose winding
is included in the line circuit, and whose contacts act directly to
start the rotary switch. In disconnecting, the rotary switch starts the
primary and the secondary connectors and thus instantly releases both
the calling and the called lines. Thereafter the rotary switch in
passing from position to position restores switch after switch of the
connective division to normal and finally itself returns to normal in
preparation for its assignment to service in answering a subsequent
call.

CHAPTER XXXI

THE AUTOMANUAL SYSTEM

Two systems of telephony are now in common use in this country--the
manual system and the automatic. With the growth of the automatic, and
the gradually ripening conviction, which is now fully matured in the
minds of most telephone engineers, that automatic switching is
practical, there has been a growing tendency toward doing automatically
many of the things that had previously been done manually. One of the
results of this tendency has been the production of the _automanual_
system, the invention of Edward E. Clement, an engineer and patent
attorney, of Washington, D. C. In connection with Mr. Clement's name, as
inventor, must be mentioned that of Charles H. North, whose excellent
work as a designer and manufacturer has contributed much toward the
pr