FIGURE 40. Simplified Common-Battery
Similarly, the two ring conductors are connected, and their junction is connected to the negative battery bus through a
similar filter network. The sleeve conductors are shown not connected. Actually, they are used for connection to
(2) Each of the cords is connected at its free end to a plug containing three contacts. The contacts of the plug also
are called tip, ring, and sleeve, from which the cord conductors connected to them derive their names. The plug at the end
of the answer cord is called the answer plug, and is used by the switchboard operator in answering a call originating at the
calling telephone station. The plug at the end of the call cord is known as the call plug; it is used by the operator to
complete the connection to the called telephone station.
b. Line circuits.
(1) As in a local-battery system, a connection between two telephone stations in a common-battery
system is completed by means of a cord circuit through the line circuits associated with the two telephone stations. In