Abstract: A time-sharing switch is connected to a speed adjuster conforming to the CCITT V.110. R reference point speed adjusters are linked with the switch. These components are controlled by a central controller so as to set a speed between the R reference point speed adjusters and the switch and a speed of the speed adjuster. A user speed is restricted to be less than the communication speed between the R reference point speed adjusters and the switch. This enables a plurality of non-ISDN terminals to conduct bi-directional communications therebetween. As a result, there is provided a multiple communication speed converting apparatus which allows a plurality of non-ISDN terminals of various speeds to communicate with the ISDN at 64 kbps in the synchronous and asynchronous modes according to the V.110 procedure of the CCITT recommendations.