erly balanced, be placed near the ends of the cores
of M1 and M2, as shown in Fig. 2, it may assume the position
indicated by either the full or dotted lines, depending upon which
of the magnets, M1 or M2, was last magnetized. The position of
this armature will serve to indicate the push button from which
the bell was operated. The magnets should be placed inside a case
and the indication may be made by a pointer attached to the shaft,
supporting the armature.

If you are able to secure the electromagnets from a discarded
electric bell they will work fine for the magnets M1 and M2. They
should be disconnected from their iron support and mounted upon
some non-magnetic material, such as brass or copper, making the
distance between their centers as small as possible. The piece of
metal upon which the magnets are mounted should now be fastened,
by means of two wood screws, to the back of the board, shown in
Fig. 6, that is to form the face of the annunciator. It should be
about 1/8 in. thick, 1/2 in. wide and long enough to extend a
short distance beyond the cores of the magnets M1 and M2. Drill a
1/16-in. hole through its center, as shown in Fig. 2. Drive a
piece of steel rod into this hole, making sure the rod will not
turn easily in the opening, and allow about 1/2 in. of the rod to
project on one side, and 1-1/2 in. on the other side.

Drill a hole in the board upon which the magnets are mounted so
that when the long end of the rod carrying the armature is passed
through the hole, the armature will be a little more than 1/16 in.
from each magnet core. The short end of the rod should be
supported by means of a piece of strip brass bent into the form
shown in Fig. 3.

Drill a hole in the center of this piece, so the rod will pass
through it. When the armature has been put in its proper place,
fasten this strip to the board with two small wood screws. You may
experience some difficulty in locating the hole in the board for
the rod, and it no doubt would be best to drill this hole first
and fasten the magnets in place afterwards.

Two small collars should be fastened to the rod to prevent its
moving endwise. Fit the collars tightly on the rod to hold them in
place.

Cut the long end of the rod off so it projects through the face of
the annunciator about 5/8 in. Take some very thin sheet brass and
cut out a needle or indicator as shown in Fig. 4. In a small piece
of brass drill a hole so it will fit tight on the othe