How do they get warning beacon lights to flash in sequence along stretches of roadworks?

I noticed that along stretches of road on the motorways in the UK, that each traffic cone has an amber highways lamp on top. These lights flash in sequence, one after the other, giving a long line of consecutive flashing traffic cones. But how do they make them flash one after the other with such precise timing? Do they switch them on manually, or are they somehow electronically linked?

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).