The Black Box CL1090A-F is a compact RS-232-to-Current-Loop converter that bidirectionally transmits data between RS-232 interfaces and 20-mA Current-Loop devices. It features a DB25 female connector at the input and a terminal block at the output, enabling flexible integration into existing industrial or telecommunications-based systems. The optical galvanic isolation ensures secure and interference-free data transmission, especially in environments with high electrical noise or differing ground potentials. The converter supports both active and passive operating modes of the Current-Loop protocol, making it suitable for a wide range of application scenarios. It is factory-configured as RS-232 DCE, but can be switched to DTE mode using the Asynchronous Modem Eliminator (ME212) to enhance compatibility with various devices.