This ETS specifies the technical characteristics required for end-to-end interworking over the Public Switched Telephone Network (PSTN) of 9600 bits or 4800 bits modems standardized for use over the PSTN, in accordance with CCITT Recommendation V.32 [2]. The objective of this specification, the application of which is entirely voluntary, is to provide the users with an added degree of assurance that modems in compliance with this specification can interwork with each other, under most network conditions.