Amphenol FCI Basics Modular Jacks include single and multi-port solutions that are widely used in Telecom, Data, Networking and Home Entertainment markets for various applications. The product features a simple, flexible and low profile design for LAN application, in particular, the Network Interface Card. Modular Jacks Cat 3 supports the transmission of 16Mbps signals targeted to phone, modem, POS terminal machines and Cat 5 supports the transmission of 100Mbps signals targeted to switch, router, hub, etc.