This Recommendation was revised to remove text that referred to international analogue exchanges. The ITU-T no longer recommends the placement of new or continued operation of analogue international exchanges. Additionally, this Recommendation was written so as to recognize that both Plesiochronous Digital Hierarchy/Synchronous Digital Hierarchy (PDH/SDH) and digital ATM switching technology may be used in the PSTN. This Recommendation provides transmission performance planning guidance for digital exchanges.