en made
with these heavy rigid terminals by means of solder. A coil having
such terminals is shown in its finished condition in Fig. 100.

_Winding Data_. The two things principally affecting the manufacture
of electromagnets for telephone purposes are _the number of turns in a
winding_ and _the resistance of the wound wire_. The latter governs
the amount of current which may flow through the coil with a given
difference of potential at its end, while the former control the
amount of magnetism produced in the core by the current flowing. While
a coil is being wound, it is a simple matter to count the turns by any
simple form of revolution counter. When the coil has been completed it
is a simple matter to measure its resistance. But it is not so simple
to determine in advance how many turns of a given size wire may be
placed on a given spool, and still less simple to know what the
resistance of the wire on that spool will be when the desired turns
shall have been wound.

TABLE IV

Winding Data for Insulated Wires--Silk and Cotton Covering

A.W.G. B & S | 20 21 22 23 24 25
---------------------------------------------------------------------
DIAMETER |
Mils | 31.961 28.462 25.347 22.571 20.100 17.900
---------------------------------------------------------------------
AREA |
Circular Mils | 1021.20 810.10 642.70 509.45 404.01 320.40
---------------------------------------------------------------------
DIAMETER OVER |
INSULATION |
SINGLE |
COTTON | 37.861 34.362 31.247 28.471 26.000 23.800
|
DOUBLE |
COTTON | 42.161 38.662 35.547 32.771 30.300 28.100
|
SINGLE SILK | 34.261 30.762 27.647 24,871 22.401 20.200
|
DOUBLE SILK | 36.161 32.662 29.547 26.771 24.300 22.100
---------------------------------------------------------------------
TURNS PER |
LINEAR INCH |
SINGLE |
COTTON | 25.7 28.3 31.0 34.4 36.9 38.0
|
DOUBLE | 22.5 24.5 26.7 28.97 31.35 33.92
COTTON |
|
SINGLE SILK | 27.70 30.97 34.39 38.19 42.37 47.02
|
DOUBLE SILK | 26.22 29.07 32.11 35.53 39.14 42.94
---------------------------------------------------------------------
TURNS PER |
SQUARE