This adapter allows you to connect an RJ11 telephone connector to an RJ45 connector. This adapter would typically be used in installations that only have RJ45 connectors, but where you want to use a telephone with an RJ11 connector. All four pins in the RJ11 connector are wired straight through to the four middle pins in the RJ45 connector. This means that the connector is universal, and can also be used for ISDN, etc.
Sandberg Adaptor, RJ11-M to RJ45-F. Gender: Male/Female, Connector(s): RJ11-M to RJ45-F, Adapter type: telephone. Color of product: White. Package width: 0.335" (8.5 mm), Package depth: 0.0787" (2 mm), Package height: 0.492" (12.5 mm)