Telephones are generally very reliable, but they can be destroyed by power surges coming from the phone line. Telephone warranties usually don't cover damage from surges, and the loss of of a telephone can be devastating for a business and extremely inconvenient for a family. Your modem is the most susceptible place a surge can strike your computer. It is absolutely crucial to protect your telephone/data line with a BT Surge Protector. Surges and spikes travel through AC and telephone lines and can damage your computer, modem, data, telephone and other valuable connected equipment.