V2020 is two E1 MUX, provides 2.048Mb/s 2 wire loop port, 4 wire E/M interface, RS232, V.35or G703port, ISDN-U port and 10Base-T port. It applied both in point-to-point and chain network. V2030 is 64?E1 DXC MUX, provides 64x2.048Mb/s 2 wire loop port, 4 wire E/M interface, RS232, V.35or G703port,2B+DISDN port and 10Base-T port. It applied both in point-to-point and chain network. V2030 NMS set as through central point PC to manage local/remote device. V2010 is 16?E1 DXC MUX, provides 16?2.048Mb/s 2 wire loop port, 4 wire E/M interface, RS232, V.35or G703port,2B+DISDN port and 10Base-T port. V2021 provides optic port, two E1 port, 10Base-T port, V35 port, V.24 port, ISDN-U port and multi voice port. V2040A: One V.35, one V.24 and one 10BaseT interface V2053 is protocol converter between RS232 and TCP/IP, provides data transparent transmission from RS232 to TCP/IP and TCP/IP to RS232.