Abstract: A data communications system in which a PAD service host that gives service to non-packet terminals (NP-DTE) via a PAD (packet assembly and disassembly) is connected to a packet switching network that has PAD with packet assembling/disassembling function and protocol conversion function for the NP-DTE, and wherein a computer system that executes the TSS service is further connected to the packet switching network. The computer system is equipped with PAD emulation function that exists between the TSS and the packet switching network and that works in the same manner as the PAD for the TSS terminals and PAD service host, whereby the service of the PAD service host can be received through the TSS terminals.