Chapter VI

Three-wire return call system--Installing elevator
annunciators--Burglar alarm annunciators--Clock
alarm circuit--Bells for high voltages--Bell-ringing
transformers--Combination bell, door opener and telephone
circuits--Fire alarm circuit--Interior fire alarm
system--Fire alarm system for considerable areas 64

LIST OF ILLUSTRATIONS

FIG. PAGE
1 Electric bell, push, and battery x

2 Leclanche cell 1

3 Dry cell 4

4 Gravity cell 5

5 Vibrating bell 10

6 Single stroke bell 10

7 Shunt or short circuit bell 10

8 Continuous ring bell 13

9 Waterproof bell 14

10 Dome gong 15

11 Tea gong 15

12 Cow gong 15

13 Sleigh bell gong 15

14 Spiral gong 15

15 Relay and circuit 16

16 Door push 19

17 Pear push 19

18 Door push 19

19 Wall push 19

20 Floor push 20

21 Door pull attachment 22

22 Wire joint first operation 25

23 Wire joint second operation 25

24 Wire joint insulating 25

25 Section of house showing wiring 29

26 Bell with ground return 30

27 Pushes in multiple 31

28 Bells in series 31

29 Bells in multiple 31

30 Two bells and two pushes 32

31 Two bells and two pushes 32

32 Two bells, two pushes and one battery 33

33 Double contact push 33

34 Grounded bell 34

35 Tongue test of wiring 38

36 Knife test of wiring 38

37 Knife test of wiring 39

38 Metallic thermostat 40

39 Mercury thermostat 41

40 Mercury thermostat circuit 42

41 Water level alarm 44

42 Lever water level alarm 45

43 High or low water level alarm 45

44 Window spring for burglar alarm 47

45 Burglar alarm--closed circuit 47

46 Special bell connection for burglar alarm 48

47 Special bell connection for burglar alarm 49

48 Burglar alarm and relay 50

49 Window-shade contact spring 51

50 House wired for burglar alarm 52

51 Door trip alarm 53

52 Annunciator drop 55

53 Needle drop 56

54 Needle drop indicating 56

55 Pendulum drop 57

56 Annunciator drop circuit 58

57 Simple annunciator circuit 59

58 Annunciator and fire call circuit 60

59 Single-wire room and fire call 61

60 Three-wire return call circuit 65

61 Elevator bells and annunciator circuit 67

62 Burglar alarm annunciator circuit 69

63 Clock alarm circuit 71

64 Bell-ringing transformer 73

65 Bell-ringing transformer with three secondary voltages 73

66 Western Electric interphone system 75

67 Western Electric interphone system for more extensive
service 77

68 Fire alarm circuit 79

69 Interior fire alarm circuit 81

70 Fire alarm circuit for considerable areas 82