The TCDT1124 is a single-channel optocoupler from Vishay (or equivalent source) in a 6-DIP through-hole package, built around a DC-input IR LED and a phototransistor output. Its headline rating is 5000Vrms of galvanic isolation, which covers reinforced insulation requirements for mains-connected power supplies, motor drives, and industrial PLC I/O modules. The 160% to 320% current transfer ratio at 10mA forward current gives you a solid saturation margin across the -55°C to 100°C operating range — useful when driving logic inputs or low-side loads without an extra gain stage.
CTR spread and output drive — sizing the load
With a minimum CTR of 160% at 10mA If, the phototransistor can deliver at least 16mA into the output load. The output is rated for 70V collector-emitter and 50mA continuous per channel, with a Vce(sat) of 300mV max — clean logic-level drive for 3.3V or 5V rails. Rise and fall times are 4µs and 4.7µs typical, which limits switching to low-speed signals (DC state detection, relay coil drive, isolated fault flags) rather than high-speed data.