1. 6N135M Substitution Conclusion As a direct replacement, the 6N135M carries a high risk and is not recommended. While its package, isolation voltage, and maximum input/output current ratings match those of the HCNW4562, key performance parameters differ significantly, and the absence of complete datasheets for the original part prevents compatibility verification. Specifically, the 6N135M has a lower minimum Current Transfer Ratio (CTR) — as low as 7% under typical conditions — which may result in insufficient output drive capability and inadequate signal amplitude at the receiver under the same input conditions. More critically, its slower turn-off time (typically 800ns) may fail to meet signal integrity or timing requirements in circuits requiring fast response, potentially leading to system malfunction or degraded performance.