Abstract: A remote control system for data communication includes a local modem as an initiating modem and a remote modem as a responding modem coupled by an analog duplexed channel, and a pair of intermediate modems coupled by a digital duplexed channel, inserted between the initiating and the responding modes. Each intermediate modem includes communication control circuitry to translate a port designation from the initiating modem into a port designation corresponding to the responding modem. Thus, the system makes it possible to simply designate a port of the remote modem to effect designation of a corresponding port of the local modem with the initiating modem having no information indicating correspondence between the port of the responding modem and those of the initiating modem.

Abstract: Receipt of a training signal by a circuit wherein a demodulated data sequence is compared with a corresponding pre-recorded sequence and an impulse produced upon coincidence therebetween, is acknowledged by two consecutive signals occuring at a time interval corresponding to the period of the data sequence.