tor, which throws the drop on his line
at the central office. The operator, seeing the signal, inserts the
answering plug of one of her idle pairs of cords into the answering jack
and throws her listening key _L.K._ This enables the operator to talk
with the calling subscriber, and having found that he desires a
connection with the line extending to Station _B_, she touches the tip
of her calling plug to the multiple jack of that line that is within her
reach, it being remembered that each one of the multiple jacks shown is
on a different section. She leaves the listening key in the listening
position when she does this. If the line is busy, the click will notify
her that she must not make the connection, in which case she informs the
calling subscriber that the line is busy and requests him to call again.
If, however, she received no click, she would insert the calling plug
into the jack, thus completing the connection between the two lines. She
would then press the ringing key associated with the calling plug and
that momentarily disconnects the calling plug from the answering plug
and at the same time establishes connection between the ringing
generator and the called line. The release of the ringing key again
connects the calling and answering plugs and, therefore, connects the
two subscribers' lines ready for conversation. All that is then
necessary is that the called subscriber shall respond and remove his
receiver from its hook, the calling subscriber already having done this.
When the conversation is finished, both of the subscribers (if they
remember it) will operate their ringing generators, which will throw the
clearing-out drop as a signal to the operator for disconnection. If it
should become necessary for the operator to ring back on the line of the
calling subscriber, she may do so by pressing the ringing key associated
with the calling plug.

Frequently this multiple switchboard arrangement was used with grounded
lines, in which case the single line wire extending from the
subscriber's station to the switchboard was connected with the tip
spring of the first jack, the circuit being continued in series through
the jack to the drop and thence to ground through a high non-inductive
resistance.

_Defects._ This series multiple magneto system was used with a great
many variations, and it had a good many defects. One of these defects
was due to the necessary extending of one limb of the line through a
large