PDH was the first digital hierarchy standard, designed primarily for transporting voice channels. The term "plesiochronous" means "almost synchronous," as network elements operate at nearly the same clock frequency but are not perfectly aligned.
: Uses bit-by-bit interleaving . To account for slight timing differences, it employs "bit stuffing," where extra bits are added to align signals. PDH was the first digital hierarchy standard, designed
: Lacks built-in facilities for automatic management and routing. Synchronous Digital Hierarchy (SDH) SDH vs PDH | Difference between PDH and SDH - Baudcom it employs "bit stuffing