a. Operating.

• The armature is attracted, and the diaphragm moves.When the armature is attracted to a certain position, it presses the point down, and the contact opens.
• When the contact opens, current flowing through the coil is interrupted and the attraction disappears. The force of the diaphragm spring returns the armature, and the contact once again closes.
• This action is repeated approximately 400 times per second to vibrate the diaphragm and generate sound. The number of repeats is termed the fundamental frequency, and this determines the pitch of the sound (tone).

 b. Differences between a flat horn and trumpet horn

• Flat horns use a vibrator to amplify sound according to its resonance.
• Flat horns are constructed so that the air gap is narrow, and the armature collides with the core. The impact force generated from the collision creates higher harmonic components that resonate at a number of times the fundamental frequency, and this energy excites the vibrator, making it resonate and amplifying the sound pressure.
• Flat horns amplify by resonating this kind of mechanical collision force, so they have a sharp frequency characteristic and highly efficient amplification, making them the most compact type of horn. In addition, they have a sharp and stimulating timbre that is very effective for warnings

(2) Trumpet horns

• Trumpet horns use the resonance of a trumpet to amplify sound.
• Because there is no need for the armature and core to collide as in a flat horn, trumpet horns have a wide air gap. The repeated vibrations of the diaphragm are converted to sound in the air chamber, and these sounds amplify as they resonate along the length of the trumpet.
• In contrast to the sharp peak frequency characteristic of flat horns, trumpet horns have wide and gradual frequency components, resulting in a soft-timbered sound