The Cisco Interface Flexibility (I-Flex) approach combines SPAs and SPA interface processors (SIPs), providing an extensible design that enables service prioritization for data, voice, and video services. Enterprise and service provider customers can take advantage of improved slot economics resulting from modular port adapters that are interchangeable across Cisco routing platforms. The Cisco I-Flex design maximizes connectivity options and offers superior service intelligence through programmable interface processors that deliver line-rate performance. I-Flex enhances speed-to-service revenue and provides a rich set of quality-of-service (QoS) features for premium service delivery while effectively reducing the overall cost of ownership. This data sheet contains the specifications for the Cisco 2- and 4-Port Clear Channel T3/E3 SPAs Version 2.

The Cisco Clear Channel T3/E3 SPAs Version 2 are designed to provide direct connectivity to T3/E3 lines for full-duplex communications at the T3 rate of 44.736 MHz or E3 rate of 34.368 MHz. They are available in 2- and 4-port options. The ports are configurable as either all T3 or all E3. To support the widest range of operational environments and to offer the greatest flexibility in provisioning clear channel T3/E3 connections, the Cisco Clear Channel T3/E3 SPAs Version 2 take a groundbreaking step and bring together proprietary subrate and scrambling features of T3/E3 DSU vendors Quick Eagle Networks (formerly Digital Link), Larscom, ADC Kentrox, Adtran, and Verilink. Subrate support in the Cisco Clear Channel T3/E3 SPAs Version 2 maximizes the application of these products in service provider environments for tiered T3 services. By simultaneously supporting interoperability with a wide range of third-party DSU vendors, the Cisco Clear Channel T3/E3 SPAs Version 2 offer the flexibility to support installed equipment without committing customers to a proprietary solution.

The Cisco Clear Channel T3/E3 SPAs Version 2 are hot-swappable and support service-transparent online insertion and removal (OIR), allowing removal of the SPA without affecting the interface processor and other SPAs.

The Cisco Clear Channel T3/E3 SPAs Version 2 can be used to provide direct customer access or network-to-network connections. In some cases, T3/E3 offers the only high-speed service to remote points of presence (POPs) or customer installations that cannot obtain optical channelized service.

The Cisco Clear Channel T3/E3 SPAs Version 2 support three different Layer 2 encapsulations of packets:
- Point-to-Point Protocol (PPP)
- High-Level Data Link Control (HDLC)
- Frame Relay
By supporting these three encapsulations, the Cisco Clear Channel T3/E3 SPAs Version 2 enable the Cisco 7600 and Cisco ASR 1000 and ASR 9000 Series Routers to offer high-speed, IP-based direct access or IP-over-Frame Relay deployments.