Appeal No. 2001-2019
Application No. 08/996,567 Page 8
capacitors 316 similarly prevent current flow to the speaker
transformers 312. Thus, the supervisory current flow is solely
through the lines 304 and 306, and through the end of line
resistor 320 in figure 6, which is the intent of the supervisory
function (col. 19, lines 35-46).
The operation of the alarm system can be readily understood
by referring to figures 2 and 6. When switch 320 in figure 2,
which is in series with the coil of relay K8, is closed, this
will give rise to operation of the flashing lights 310 only of
alarm units 308 (col. 18, lines 6-11). Switch 320 is a manually
operable switch that is accessible to the operator of the system
(col. 18, lines 11-14). In the absence of an alarm signal from
terminals E and F, closing of switch 320 will cause the coil of
relay K8 to be energized, shifting the contacts of K8A and K8B to
be shifted to the opposite position. This results in +24 volts
d.c. being applied to alarm units 308, resulting in the forward
biasing of diodes 318, thus providing d.c. power to the flashing
lights 310 (col. 18, lines 14-22). Note that at this time, d.c.
current does not flow through the primary of the transformers of
speakers 312 due to the presence of capacitor 316. Although
diode 338 conducts, diodes 332 and 336 are reverse biased and are
non-conductive (col. 18, lines 22-29). If switch 320 is now
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Last modified: November 3, 2007