A standard cooling fan is essentially a bladed DC motor. By varying the voltage input across the acceptable range for a fan, the speed of the fan will increase (to added voltage) and decrease (to reduced voltage); a faster fan means more air moved and thus a higher heat exchange rate.
Contact them toll-free from a Vodacom cellphone by dialing 111. Contact them toll-free from a Telkom phone by dialing 0800-111-234. Note: Telkom toll-free numbers are generally NOT toll-free when dialed from a MTN/Vodacom cellphone.
The service, known as the Telephone Preference Service (TPS), is already used by 18.5 million (85pc) landline users, but only 2.9 million (3pc) of mobile users are signed up, Ofcom said. To sign up people must text TPS and their email address to 85095.