Transitioning from 4-Wire Leased Lines to Leased T1 or Ethernet

Telephone companies that no longer support 4-Wire audio leased lines presents an issue for utilities operating via 4-Wire leased lines.

The Scenario

As early as 2015, telephone companies no longer supported 4-Wire audio leased lines. This presents an issue for utilities currently operating their line voltage protection or SCADA equipment via 4-Wire leased lines (analog). In some scenarios, full or fractional T1 leased digital data service lines are available for a nominal monthly fee. In other scenarios, leased Ethernet service lines are available at a lesser monthly fee than T1 leased lines. Utilities are looking for a path forward that minimizes operational impact, requires little engineering, and assures comparable security and dependability for their protection and SCADA signaling. See Figure 1 (below).

The Solution

For leased T1 lines, RFL® offers a T1 multiplexer with various interfaces including 4-Wire audio that will allow utilities to continue to operate their protection and SCADA equipment with the same security and dependability. Other options include the replacement of the 4-Wire analog interface with an RS-449, V.35 or C37.94 digital interface to

For leased Ethernet lines, RFL® offers an IP Access Multiplexer with various interfaces including 4-Wire audio, RS-449, V.35 or C37.94 interfaces for the operation of legacy services over Packed-Switch Networks. The IP Access multiplexer will allow the operation of the protection and SCADA equipment with either 4-Wire analog interface or digital interface over the leased Ethernet service with the same reliability as that of the 4-Wire leased line. See Figure 3 (below).

The Results

Both the T1 multiplexer and the IP Access Multiplexers allow the migration of the protection and SCADA equipment to a digital communications link. This improves tolerance to analog noise that can disrupt operation, thereby improving the dependability of the protection and SCADA system. 

These field-proven substation solutions ensure out-of-box performance without the need to replace the units or rewire peripheral devices connected to the protection or SCADA equipment. work over the same T1 multiplexer. See Figure 2 (below). The RFL® eXmux 3500 is a substation hardened IP Access Multiplexer engineered to modernize substation communications infrastructure. Using high-speed IP transport, the eXmux platform is designed to seamlessly converge legacy Time Division Multiplexing (TDM) devices with IP-based voice, video and data between substations and control centers, guaranteeing mission critical traffic signals arrive on-time, every time. The RFL® I MUX 2 000 T 1 Multiplexer is a communications platform designed to transport mission-critical signals reliably between substations and control centers. Designed for harsh environments and mission-critical infrastructures, the IMUX 2000 family of products enables power utilities to deliver power safely, reliably and cost effectively, guaranteeing mission-critical traffic signals arrive on-time, every time.

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