If a door must be crossed the wire may either run up one side of the frame and down the other or laid beneath the carpet on the sill. The former is preferable, but takes more wire.
In many houses the bell wire as well as the battery wire may be run across the cellar beams (Fig. 25), in which case bore a second hole for it near the push; do not draw it through the same hole as the push to battery wire. And, of course, here work upwards with the spool in the cellar.
Having reached the bell location, run the third wire down into the cellar to the battery. Now connect up the push, baring an inch or so of each wire, push them through the holes provided in the push base, screw down the push base and clamp the wires under the washers through which the connection screws run. Do this neatly, be sure the ends of the wires do not stick out, cut off what is left free of the bared ends. Then connect the battery to the wire from the push and the wire from the bell. The last thing is to scrape and fasten the bell wires to the bell binding posts. Do this so that they cannot come loose and that they make good contact.
The bell should now ring properly when the push is pressed.
To sum up, one wire leads from one spring of the push to the bell, one wire from the other spring of the push to the battery, and another wire from the remaining binding post on the bell to the remaining binding post on the battery. It is immaterial whether the zinc terminal or the carbon terminal go to the bell or push.
=Combinations of Bells and Pushes.= One of the wires in a bell circuit may be replaced by the ground (Fig. 26). Connection may be made to a gas or water pipe or to a metal plate buried deep in damp earth. Any wire fastened to such a plate must be thoroughly soldered to it or a voltaic action will be set up, which will eat it away at the point of contact.
When one bell is to be rung from two or more points the pushes are to be connected in multiple (Fig. 27) as if they were in series; all would have to be closed to complete the circuit.
If two bells are to be operated from one push they may be in series (Fig. 28), but in this case one of them must be arranged for single stroke. If both were vibrating bells the armature of one would not vibrate in unison with the other armature and the result would be irregular contact breaking and intermittent ringing.