Black Box Explains... Local Multiplexors
Local multiplexors extend the distance between computers and terminals or printers that are connected via customer-installed or telco-supplied cable.
Like line drivers, local multiplexors extend RS-232 communications and must be used in pairs. The difference between the two is that multiplexors merge several transmissions into one transmission over a single channel; line drivers generally transmit data over a single channel.
Local multiplexors operate over ordinary twisted-pair copper cable or fiber optic cable. Copper cable is typically used within buildings while fiber optic cable is the most common choice for connecting buildings in a campus environment. For in-building connections, copper cable is widely used because it’s comparatively inexpensive and easy to install. Your building might even have unshielded twisted-pair cable already in place.
The twisted-pair copper cable used for local multiplexors is run throughout buildings from the wallplates of each office or work area to a central wiring closet within the building. Wiring closets have centrally located punchdown blocks where all cables from the building are terminated. That way, when a connection needs to be changed or a new one needs to be made within the building, wiring can be easily rerouted on the punchdown blocks.
Selecting a local multiplexor.
When selecting a local multiplexor, keep in mind that copper-based multiplexors come in a vast array of types. You’ll find multiplexors available with RJ-11, RJ-45, or terminal block connections for your in-house wiring and with RS-232 connections for your computer equipment. All these multiplexors can be used to link a local device to a remote device within a building.