This cable can be used between an analogue modem and an ordinary telephone. Or between a telephone/modem and a wall socket with an RJ11 or RJ45 connector.
Sandberg Telephone RJ11-RJ11 1.8 m BL
Sandberg Telephone RJ11-RJ11 1.8 m BL. Cable length: 70.9" (1.8 m), Color of product: Black. Package width: 2.76" (70 mm), Package depth: 1.57" (40 mm), Package height: 6.57" (167 mm). Connector(s): RJ11/RJ45