PDH (Plesiochronous Digital Hierarchy)

Plesiochronous Digital Hierarchy (PDH) is a telecommunications network standard used to transmit large amounts of data over fiber optic or copper cables. It combines multiple digital signals into a single, higher-capacity signal while maintaining synchronization, allowing various systems to communicate effectively. PDH uses specific rates for data transmission (like 2 Mbps or 34 Mbps) and helps manage and switch these data flows across networks. Although largely replaced by more advanced systems like Synchronous Optical Network (SONET) and Synchronous Digital Hierarchy (SDH), PDH laid the groundwork for modern digital communication systems.