This adapter converts an RJ11 connector, typically found on an analogue telephone, to a wider RJ45 connector, which is often used in companies with switchboards.
Sandberg Adapter RJ11 Fem - RJ45 Male. Gender: Male/Female, Connector(s): RJ11 Fem - RJ45 Male, 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)