Editing Synchronous optical networking (section)

===Add-drop multiplexer===
[[Add-drop multiplexer]]s (ADMs) are the most common type of network elements. Traditional ADMs were designed to support one of the network architectures, though new generation systems can often support several architectures, sometimes simultaneously. ADMs traditionally have a ''high-speed side'' (where the full line rate signal is supported), and a ''low-speed side'', which can consist of electrical as well as optical interfaces. The low-speed side takes in low-speed signals, which are multiplexed by the network element and sent out from the high-speed side, or vice versa.