TYPE 4208 “L.”
SERIES DC SIGNAL PANEL
.
INTRODUCTION
The “L” panel is elesigned to operate series con- normal operation. Each panel has its own power
netted, single stroke DC bells or chimes. All signal supply and can operate two signal circuits or each
circuit wiring and signal coils are supervised during circuit can be activated separately.
CIRCUIT OPERATION (FIG. 15)
Normal Operation
During normal operation, relay Kl is energized
and supervisory current -24VDC flows from the
rectifier through contacts KlB (6&10) to terminal
-24 where the current flow splits into two paths.
One path is from terminal -24, to PC7 on the
Trouble Module.
The other path is from terminal -24, through re-
sistor R2, contact K3D (4&12), terminal G2+, ter-
minal G2A+, the series signaling devices, terminal
G2A-, rheostat R4, terminal G2;fuse F5, contacts
K3A (9&l), resistor Rl, contacts K2A (l&9), ter-
minal Gl+, terminal Gl A+, the second circuit of
series signaling devices, terminal Gl A-, rheostat
R3, terminal Gl-, fuse F4, contacts K2D (128~4) to
PC4 on the Trouble Module. Current flows through
the Trouble Module and out PC2 to terminal +24.
Trouble ModuZe
- (Fig. 16)When -24VDC is ap-
plied to PC4 from the signal circuit, current flows
through diode Dl and resistor R4 and a negative
potential is applied to the base of transistor Ql
turning Q 1 on.
With Ql “on” a positive potential is applied to
the base of 42 (from PC2 via Rl and Q 1) keeping
42
“off.”
With 42 “off’, a negative potential is applied to
the base of 43 keeping 43 “off” (from PC7 via R6,
R7).
Power Failure Condition (Fig. 15)
If a power failure occurs, relay Kl de-energizes
and its contacts transfer. The -24VDC from termi-
nal -BAT is applied to terminal 5 through contacts
Kl A (l&9) and diode D2 which causes a “trouble”
condition in the “A” panel. Also, -24VDC is ap-
plied to the panel to provide power for normal
operation. Current flows from terminal -BAT,
through fuse F3, contacts K 1D (4&l 2) to terminal
-24. Contacts KlB and KlC perform the same
function as the KID contacts.
Trouble Condition (Fig. 16)
If an open occurs in the signal loop, the negative
potential (from PC4) is removed from the base of
Ql which turns “off” Ql.
With Ql “off”, a negative potential is applied to
the base of Q2 which turns “on” Q2 (-24VDC from
PC7 via R5). When Q2 is “on” a positive potential
is applied to the base of Q3 which turns “on” Q3.
31
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