Electric bells are often objectionable as signal calls because of their clamor, but with the removal of the bell the vibrating armature serves equally well as a signal but without the undesirable noise. With the bell and tapper removed the operating mechanism of such a device works with a sound that has given to them the name of buzzers. Fig. 241 illustrates the form of an iron-cased buzzer for ordinary duty. The working parts are enclosed by a stamped steel cover that may be easily removed. The mechanism is quite similar to that already described in the doorbell and Fig. 240 shows in detail the working, parts. The noise, from which the device takes its name, is produced by the armature and spring in making and breaking contact.