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A Symbolic Analysis of Relay and Switching Circuits

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15<br />

therefore necessary to manipulate the expression into<br />

the form in which the least numb~r<br />

<strong>of</strong> letters appear.<br />

The theorems ~iven<br />

above are always sufficient to do<br />

this.<br />

A ].1ttle practice in the manipulation <strong>of</strong> these<br />

s;rm1:o1s is 811 that is required.<br />

Fortunately most <strong>of</strong><br />

the theorems are exactly the same as those <strong>of</strong> numerical<br />

al~eora--the associative, commutative,<br />

<strong>and</strong> distribut1ve<br />

laws <strong>of</strong> algebra hold here.<br />

The writer has found<br />

theorems 3, 6, 9,14, 15, 16a, 17, <strong>and</strong> 18 to be especlally<br />

useful in the simplification <strong>of</strong> complex axpres<br />

sian s.<br />

AS<br />

a n exampl e <strong>of</strong> the 81mp11 fica tion <strong>of</strong> expressions<br />

consider the circuit shoWn in Fi~. 5.<br />

~.-.<br />

5'<br />

v<br />

y<br />

_-.....--0 0---0 •<br />

~ WI<br />

Fi Q;. 5<br />

•<br />

x<br />

o<br />

z'<br />

...... '0<br />

Z<br />

The hind'3rance function X ab<br />

for this circllit<br />

will be:<br />

X ab<br />

= W+\\II(X+Y) + (X+~HS+W'+e)(~'+Y+S'V)<br />

,<br />

~ "i\[<br />

= ~+X+Y+(X+~)(S+l+g)(gl+Y+stV) v<br />

= W+X+y+g(~'+S'V)<br />

lthesa reductions walee made \'V1"tth 17b using first ~N,<br />

then X <strong>and</strong>

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