Page:Popular Science Monthly Volume 89.djvu/293

 Popular Science Monthly

��279

��Five Examples of Alarm Work

THIS may be done by arranging the circuits as shown in Figs, a, b, c, d, e. lisiiaily when it is neccssar\' to employ a constant ringing meliiod on a call system, an anniiiuiator is also installed and a point proxided on the annunciator for each placi' wlu-re This is shown in all In Fig. (a), a

��a call is turned in. of the diagrams.

��constant ringing bell is used. This type of bell is a combination of the vibrating bell and the automatic drop. Its opera- tion is as follows: the circuit is taken through the push- button and a point on the annunciator, then through the coils in the bell and back through the battery. This causes the arma- ture to be drawn in and allows the drop to fall, com|)leting another circuit through the bell, the connection be- ing from line to bell to line. This will cause the bell to ring as long as there is enough cur- rent in the battery.

In Fig. (b) prac- tically the same operation takes place except that the bell and the drop are separate.

In Fig. (c) the diagram is based on another princi- ple. When the push- button is closed, current flows through the coil of tile relay. Tin- bell is jKirallel with the relay. This will cause the armature to be drawn up,

��Annunciator

��closing the circuit through the armature of the relay and llie frame. This will close a circuit through the coils on the re- lay and the bell continually. As there is a circuit through the coils the armature will be drawn u[) and held there as long as the current Hows.

In Fig. (d) is illustrated a closed-circuit

alarm. To be adapted to a call system

it must be con-

���Constant Rinqinq Be// ^

��Open Circi/it Battery

��Anni/nc/a/ar

���Ope/7 Orcc/// Aii/orno//c Drop

6

��P'//?ra//r7g ~ Be//

��A/arm Conroc/s

��Open Orcui/ Bofferu

���Insulated Po/nf

��tT/bratiny Be//

��Closed C/rcuil Ba/lin

��^Double Pole S/xip 5wlch to sefAlam, mm

��Bell

��Open Circuif B<7/rery

��''~-Tf)i5 poi'1/ /s Insu/a/ed from frame but not from armj/ure

Srrltc/tes A,BIC nlll not s/cp t>el/, once a/cu/f /las i?een opened

��ellQ Upen Orcuif local 8a/liry

��riq d

��"S

��/nsuia/ed fb/l Te/eynfp/y Pe^\ AnnorK/ofor ■2^

���P/a//num Pcvnt

This point IS insviT/b/ from fran?e butna from arma/ure yi/mi/ino 3f//

��Alarm

��-Dool>le f^/e Snap Suite/? Contacts Closed Circuit Battery /o reset A/arm

Fi^ e

Wiring diagrams of a five-bell electric annunciator system

��nected as shown in Fig. (e). The current flows through the contacts and the coils of the relay to the armature of the relay to the frame of the relay and back to the battery. The plat- inum point of the relay is toward the coils and the arma- ture must be drawn over toward the coils before the cir- cuit is complete. Once completed it will be held by the action of the arma- ture. A switch is provided for clos- ing the circuit. The bell is connected across another bat- tery, although it could be connected through the same one. The current for the bell passes through the arma- ture of the relay and the e.\tra plati- num [loint on the relay which is in- sulated from the frame. As the cir- cuit through the contacts is broken, the spring will pull the armature away from the contact point toward the coil and against the contact point to which the bell is connected.

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