A rotary dial is a mechanical device found on older telephones, used to input phone numbers by rotating a numbered disk. Each number is selected by inserting a finger into the corresponding hole and rotating the dial to a fixed stop. Upon release, the dial returns to its original position, generating a series of electrical pulses corresponding to the chosen number. These pulses are sent down the telephone line to the exchange, allowing the call to be routed. While rotary dials are not directly related to modern cybersecurity, understanding legacy technologies is important for securing older communication systems and recognizing potential vulnerabilities that may still exist in outdated infrastructure.