Richard wrote: I've never participated in the past terminal server/mux conversations, but I happen to have a fair bit of experience with all types of this legacy equipment. The description is of course really weak, so I can only provide some educated guesses. This appears to be an async serial multiplexer. These were pretty popular at one point, and allowed several async serial rs-232 terminals & printers to communicate across a single SYNC composite WAN interface --- normally a 56K DDS circuit, or a fractional T1 --- depending on the capacity/baud rates/compression, etc. You can clearly see what looks like DB25 connectors, are those males? Anyways, the (24) ports are DB25's, where you'd hook up your serial devices.... There are also RJ21 Telco connectors -- these would be to simplify cabling to a patch panel, which might have matching telco connectors, so you don't have (24) thick cables running all over the place. Upper right hand corner connectors are probably the DB15 connectors which are probably to go to your WAN circuit, in this case, maybe a T1? It may actually support DROP and INSERT because of the two different RJ45's. Maybe DB15 with optional RJ45 if you want it. Lower right hand corner has DB25's, and those would be the composite SYNC serial connections for going to a T1 channel bank, or external CSU. Obviously if the top is a built-in CSU/DSU, the lower right connectors would likely not be used. (could also be just a built-in CSU, but requiring external DSU) One of the DB9's and/or one of the DB25's lower right connectors would be the console management serial interface -- for either hooking up a dumb terminal for configuration, or attaching a modem for remote configuration across a dialup modem. Last, but not least, the description says it has (24) 2-wire FXS cards. FXS is a phone interface for attaching directly to a regular analog phone, but I see no corresponding connectors on the box. There should be a bunch of individual cards with RJ-11's or perhaps terminal strips or something on them. I do see two strips, but the description just doesn't pan out --- If there are (24) cards, there should be (24) cards, and I just don't see them in the picture. (maybe not pictured??) Most muxes are not useful by themselves. They often encapsulate the ASYNC data coming from the DB25 connectors into a proprietary HDLC-like synchronous serial stream that traverses the connection --- and then you have a matching unit break that stream out on the other side. Last thing: its description says it's a PCM mux --- which usually indicates voice (analog voice into digital, across a T1) which goes along with the other description of the (24) FXS cards --- BUT: the picture is clearly some sort of DATA-mux... The long and short: I think this would be a horrible waste of (shipping) money to buy this. YMMV. Keith