1. Isolation Voltage: H11B2 is rated at 5300 Vrms, while H11B1M is rated at 4170 Vrms. In high‑voltage isolation applications, substitution may pose a risk if the original design margin is insufficient or if the standard requirement exceeds 4170 Vrms. 2. Current Transfer Ratio (CTR): The minimum CTR of H11B1M (500% @ 1 mA) is significantly higher than that of H11B2 (200% @ 1 mA). This indicates that H11B1M offers higher sensitivity and can drive the same load with lower input current, which helps reduce front‑stage power consumption. However, care should be taken to avoid increased sensitivity to noise or temperature drift due to the higher CTR. 3. Output‑Side Parameters: H11B1M specifies a rated output current of 150 mA and a withstand voltage of 30 V, whereas H11B2 does not specify output current and has a withstand voltage of 25 V. H11B1M may offer advantages when driving capacitive loads or higher‑voltage loads, but it is necessary to verify whether the original application relies on the potential current‑limiting characteristics of H11B2. 4. Input Drive Requirement: The maximum forward current (If_max) of H11B1M is 80 mA, lower than the 100 mA of H11B2. If the original circuit drives the LED with a high current (> 80 mA), substitution could risk overloading the input side, requiring a re‑evaluation of the current‑limiting resistor. 5. Operating Temperature Range: H11B2 supports a lower limit of –55 °C, while H11B1M starts at –40 °C. For extreme low‑temperature environments (e.g., military, deep‑space equipment), H11B1M may not be suitable.