 | Circuits, Formulas and Tables Electrical Engineering - Basic vocational knowledge (Institut für Berufliche Entwicklung, 201 p.) |
 |  | 2. Bell Circuits |
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(introduction...)
The reference letters and numbers in the illustrations of bell circuits have the following meanings:
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a |
switch |
E |
voltage source |
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b |
control switch |
f |
transducer |
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c |
contactor |
g |
measuring instrument |
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d |
auxiliary contactor, relay |
h |
visual and audio alarm |
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e |
protective device |
Tr |
transformer |
2.1. Direct-current Bell
Direct-current bell to be actuated
from one place
Direct-current bell to be actuated
from two places
Bell installation for reciprocal
calls
Sell installation for reciprocal
calls with key change-over switch
Bell installation for reciprocal
calls with switch-on push-button, line-saving
Bell installation for reciprocal
calls,
line-saving
2.2. Alternating-current Bell
Alternating-current bell with bell
transformer, simple circuit
Bell installation with change-over
switch
2.3. House Bell Installation
Circuit of a house bell installation
Circuit of a house bell installation
with electric door
operator
2.4. Alarm Systems
Circuit of an alarm system with
normally open contacts b1 test key, 1 glass panel
Circuit of an alarm system with
normally closed contacts b2 test key, 1 glass
panel