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. 



