Garrett, I will use a local power supply to feed DAC and the drive of digital output, loop power will not be used. The snap is from the data sheet of DAC161S997 , I forget to modify it by deleting LDO. Digital output is pulse output, from 0 to 10kHz and external pull up to 16VDC to 30VDC, one BJT with open collector will be used behind opto-coupler. Do you want to close this thread now? I still need to find the switch used in diagram above. Regards, Ma Dawei
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