Single-stroke Bell
This bell has two coils, wound unto an insulated bobbin. The bobbins are fitted on to a U-shaped soft iron core and the magnetic circuit is completed by a soft-iron strip attached to a spring-loaded armature. The armature has the striker attached to it which hits the gong to make sound. See Fig 8.1 pg. 108 Donnelly.
Operation
1. A current passes through the coil when the button is pressed.
2. The soft-iron strip is pulled towards the electromagnet (coil)
3. The striker hits the gong (only once)
4. When the circuit is broken the coil becomes demagnetized and the armature and striker goes back to the original position.
Trembler Bell See Fig 8.2 pg. 108 Donnelly.
This is similar to the single stroke bell, with the exception of a set of variable contacts.
Operation
1. When the button is pressed the electromagnet (coil) pulls in the soft-iron strip.
2. The contacts open, the coil demagnetizes and the spring pulls the armature back to the original position.
3. This cycle repeats until the button is released.
4. The speed of the stroke can be varied by varying the contact screw.
Continuous Ringing Bell See Fig 8.3 pg. 109 Donnelly.
Operation
1. When the button is pressed the electromagnet (coil) pulls in the soft-iron strip.
2. The lever drops down on the first stroke and short circuits the push button.
3. The bell now operates as a trembler bell.
4. To stop the bell pull the cord, and the lever will reset.
This bell has two coils, wound unto an insulated bobbin. The bobbins are fitted on to a U-shaped soft iron core and the magnetic circuit is completed by a soft-iron strip attached to a spring-loaded armature. The armature has the striker attached to it which hits the gong to make sound. See Fig 8.1 pg. 108 Donnelly.
Operation
1. A current passes through the coil when the button is pressed.
2. The soft-iron strip is pulled towards the electromagnet (coil)
3. The striker hits the gong (only once)
4. When the circuit is broken the coil becomes demagnetized and the armature and striker goes back to the original position.
Trembler Bell See Fig 8.2 pg. 108 Donnelly.
This is similar to the single stroke bell, with the exception of a set of variable contacts.
Operation
1. When the button is pressed the electromagnet (coil) pulls in the soft-iron strip.
2. The contacts open, the coil demagnetizes and the spring pulls the armature back to the original position.
3. This cycle repeats until the button is released.
4. The speed of the stroke can be varied by varying the contact screw.
Continuous Ringing Bell See Fig 8.3 pg. 109 Donnelly.
Operation
1. When the button is pressed the electromagnet (coil) pulls in the soft-iron strip.
2. The lever drops down on the first stroke and short circuits the push button.
3. The bell now operates as a trembler bell.
4. To stop the bell pull the cord, and the lever will reset.