Page 248 - Electromechanical Devices and Components Illustrated Sourcebook

210 Electromechanical Devices & Components Illustrated Sourcebook

The next significant advancement in telephone technology Vibrators
was the rotary dial system. This system was designed to
allow the subscriber to call any other subscriber directly Vibrators are used in all manner of manufacturing. There are
without calling the operator. The system used a dial that pro- two principal types of vibrators—piston and rotary. Piston
duced pulses that corresponded to the number on the dial. vibrators have a permanent magnet in the center of a solenoid
The pulses were translated into certain connections with the coil, as shown in Figure 11-61. When an AC signal is applied
use of large arrays of sector relays. Figure 11-60 shows an to the coil, the magnet oscillates back and forth to create a
early dial telephone. vibration. Generally, piston vibrators are used in applications
that require high frequency and low amplitude.

Coil
Hook Switch
Coil Form

Permanent Magnet
Headset
4 5
3 6
Figure 11-61 AC Vibrator
2 7
Area Code
Rotary Dial 1 000 8
000-0000
A rotary vibrator, as shown in Figure 11-62, is simply an
0 9
electric motor with an off-center weight attached to its shaft.
By varying the speed of the motor, the frequency of the vibra-
tion can be adjusted. By changing and/or adjusting the radius
of the off-center weight, the amplitude can be adjusted.
Generally, rotary vibrators are used in applications that
require low frequency and high amplitude.
Electrical Cabinet

Electric Motor
Off-Center Weight

Hub

Figure 11-60 Early Rotary Dial Telephone Figure 11-62 Rotary Vibrator