Project Description

SEL-2506 Rack-Mount Remote I/O Module

SEL-2506 Rack-Mount Remote I/O Module

The SEL-2506 Rack-Mount Remote I/O Module has eight digital inputs, eight digital outputs, and a fiber-optic communications port.  Connect an SEL-2506 to a fiber-optic port or transceiver on a protective relay to add digital I/O. Or, wire the SEL-2506 I/O to relay I/O to add  SEL Mirrored Bits® teleprotection.


Front- and Rear-Panel Diagrams

SEL-2506 Front Panel SEL-2506 Rear Panel
Front Rear


Protection and Monitoring

Improve the security of pilot communications for existing two- and three-terminal line applications. Use local or remote trip and close coil monitoring capability. Implement simple bus protection using contact inputs and outputs from existing relays.


Expand the I/O of SEL relays that are Mirrored Bits® communications compatible. Make the I/O status from any relay available to SEL Mirrored Bits communications schemes. Use the SEL-2506 with an SEL-2100 Logic Processor for high-speed control applications.


Replace control wiring to outside cabinets with fiber-optic cable to eliminate paths for dangerous voltages. All wiring is behind the panel.

Dependability and Reliability

Add the high reliability and security of Mirrored Bits communications to your installations. Use the communications monitoring feature to alarm when fiber-optic control cabling has been damaged, disturbed, or altered.

Status Indication

Print user-configurable labels to clearly indicate I/O usage.

Easy Application and Installation

Set parameters with switches. Quickly install and remove the SEL-2506 using patented Screw-Terminal Connectorized® blocks, without disturbing wiring.


The SEL-2506 communicates with a remote device using Mirrored Bits communications. Each contact input controls one of the eight transmit bits, while each of the eight receive bits controls an output contact. Use the transmitted contact input status for control and indication at the remote device. Use the remote device to control the SEL-2506 output contacts in trip, close, and other schemes. Use two optical fibers instead of 32 largediameter wires, saving material and labor costs.

Teleprotection Application

Remote Device Control



2505 2506 2595
Save Wiring Via I/O Multiplexing
I/O for SEL Relays/SEL-3530/SEL-2100 A A
Transfer I/O to SEL-2505/2506
Transfer I/O to SEL-2594/2595
Improve Safety With Optical Fiber
Rack-Mount + +
Panel-Mount + +
Projection Panel-Mount + +
User-Configurable Labels
Screw-Terminal Connectorized Blocks
Digital Inputs (DI) Base 8 8 8
DI Maximum 8 8 8
Digital Outputs (DO) Base 8 8 8
DO Maximum 8 8 8
SEL Mirrored Bits
IEEE C37.94
Standard Feature
+ Model Option
A With SEL-3044 Encryption Card Option With compatible SEL fiber-optic transceiver or interface option or processor.

Product Literature