Appeal No. 2002-0587 Page 8
Application No. 08/922,300
signals applied to the deflection yoke. However, we find that
Martin additionally discloses a horizontal deflection yoke 17 and
vertical deflection yoke 18 (col. 2, lines 19-21). Horizontal
deflection control circuit 36 drives the beam off of the screen
when protection is required, by producing additional current
through the horizontal deflection yoke 17 (col. 3, lines 40-44).
In normal operation, the horizontal deflection of the beam is
controlled by a signal from the horizontal or X-yoke drive 101
over line 55 at the base of NPN transistor 56. A second NPN
transistor 58 is normally off and is connected across transistor
56 with a current limiting resistor 59 connected therebetween.
Transistor 58 is normally off and current through transistor 56
controls the current through the horizontal deflection yoke 17.
When it is necessary to protect screen 16, transistor 58 is
turned on and additional and additional current is drawn through
the coil of the horizontal deflection yoke 17 so as to drive the
beam off of the screen. The voltage for transistor 58 is from
either of voltage sources +V4 and +V5. These two bias voltages
are arranged so that if one fails the other will be present (col.
3, lines 44-65). Martin further discloses (col. 3, lines 65-69)
that “[t]he value of these bias voltages are chosen so that even
if the power supply fails, these voltages decay off at a slow
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