Double Circuit Experiments
Experiments 6-25 have yet to be entered. In 6-18, he experimented with the number of
cells in the battery, noting that the greater the number of cells, the lower the pitch. The
problem is that if he adds batteries to boost the power for long-distance transmission,
he will distort the signal. Bell eventually cuts a and b out of the circuit and uses a
permanent magnet in place of the armature in the transmitter slot (see "Double Pole
Transmitter" level for sketches that show the different rotations of the magnet he tried).
If he could get one of these permanent magnet designs to work, he could induce a
current and, therefore, avoid the problems associated with batteries altogether. He also
appears very interested in getting a tone from the helix alone, something he did in
November of 1874 (see "Molecular Vibration Helix Experiments" level). As always, Bell's
experiments are directed as much at understanding as at building a practical circuit.
This level illustrates how a slot diagram can be used as a basis for depicting and
studying the fine-grained details of an inventor's processes. For a more complete
example, see the levels just below the bottom two boxes on the top level of the Bell
map (the "Master Map"), which show the experiments that led to the first transmission of speech.
Copyright (c) 1994 by Michael E. Gorman, all rights reserved.
Last Modified: Sunday, 20-Nov-1994 22:02:07 EST