MD-21 20 mA Current loop converter … Conversion between 20 mA current loop and RS-232 … Galvanic isolation … Transient suppression … Code independent/transparent … Transmitter and receiver can be configured as active or passive … Ensures communication over long distances and in environments with high levels of interference … AC-/DC-supply … Reliable performance and function Field of application 170 MD-21 is used in point-to-point applications where interface conversion from a 20 mA current loop to RS-232 is required to permit communication between different devices. In some cases the converters are used for connection in loops, these are then limited to a total of 6 connected devices. The converter can be set “active” to supply the line with current or “passive” depending on how the connected device is configured. Date rates up to 19.2 kbit/s and transmission ranges up to 6 km (3.73 mi) are possible depending on the data rate. MD-21 is intended for mounting on a 35 mm DIN-rail, where the modem is attached and locked in a single action. Converter, 20 mA current loop www.westermo.com

Application Also see application on page 45 Interface DIP-switches Accessible under lid RS-232 Up to 19.2 kbit/s LED indicators RS-232 Up to 19.2 kbit/s 20 mA current loop Up to 19.2 kbit/s Power Operating voltage Rated current Rated frequency Connection www.westermo.com MD-21 AC 207 – 264 VAC 22 mA @ 230 VAC 48 – 62Hz Detachable 3-pos. screw terminal MD-21 115 AC 103 – 132 VAC 44 mA @ 115 VAC 48 – 62 Hz Detachable 3-pos. screw terminal MD-21 DC MD-21 36 – 55 DC 12 – 36 VDC 36 – 55 VDC 140 mA @ 12 VDC 50 mA @ 36 VDC DC DC Detachable 2-pos. Detachable 2-pos. screw terminal screw terminal Converter,...