The AT&T Long Lines network predates the use of digital radio for telecommunications. It used analog FDM to carry multiple calls. These towers have lasted becau

The AT&T Long Lines network predates the use of digital radio for telecommunications. It used analog FDM to carry multiple calls. These towers have lasted because they, and the radio equipment, were designed to survive a nuclear war. (Another reason the fiber transition happened quickly was that fiber was more survivable.) There are many new microwave links being deployed now using modulation techniques for digital data.