3-Port Modem Splitters (MS-3)
By Black Box

Both models include DB25 extension cable and a serial AT adapter. - Modem sharing for three to six users. - Perfect for workgroups that need limited data communications or only connect to the Internet occasionally. - Inexpensive, nonpowered, easy to use. - Use with sync or async devices. ... 

Straight Thru Modular Coupler RJ11F/RJ11F
By Tripp Lite

This coupler provides a simple and easy way to link together two cables with RJ11 plugs. The coupler is wired in a straight through configuration. RJ11 female to RJ11 female. Tripp Lite warrants this product to be free from defects in materials and workmanship for life. ... 

16-Port JetStream8516 - 10/100 RJ45 RS232 Rack-mount
By Perle Systems

JetStream 8516 Terminal Server offers a cost effective and efficient way of communicating with serial devices over a LAN or WAN. JetStream provides 16 serial ports that can access or be accessed by various systems across a network. This eliminates the need for multiple servers with serial port cards and reduces costly cabling. ...