WebX.21 adaptor for a Japanese NEC PC-98. X.21 (sometimes referred to as X21) is an interface specification for differential communications introduced in the mid-1970s by the ITU-T. X.21 was first introduced as a means to provide a digital signaling interface for telecommunications between carriers and customers' equipment.
WebX.21 is a state-driven protocol running full duplex at 9600 bps to 64 Kbps with subscriber networks. It is a circuit-switching protocol using Synchronous ASCII with odd parity to connect and disconnect a subscriber to the public-switching network. The data-transfer phase is transparent to the network.
WebX.21 is a state-driven protocol running full duplex at 9600 bps to 64 Kbps with subscriber networks. It is a circuit-switching protocol using Synchronous ASCII with odd parity to connect and disconnect a subscriber to the public-switching network. The data-transfer phase is transparent to the network.