The Cisco 2600, 2800, 3700 and 3800 Series offer a wide variety of serial connectivity modules to accommodate the range of application needs in customer networks. The serial network module family assures customers that they can choose a serial connectivity solution that fits their requirements. Serial connectivity options offer several port densities, synchronous and asynchronous alternatives. As modular components, they are easily and inexpensively field upgradeable as customer requirements change.