Hi, I have an electrically-actuated shutter that can be either in the "closed" or "open" positions. I want to use optoelectronic switches (slotted switches with an infrared LED source and photodiode detector) at either end that will detect whether the shutter is closed or open. The opto switches I am looking at come in either the open collector output or totem pole output variety (both common output stages used in the TTL logic family, from what I gather). I basically have to make a choice between one or the other. From what I can tell, applications of open collector outputs are the ability to connect the output through a pull up resistor to a supply that is *different* from the chip supply (if interfacing two different kinds of devices). Another application I read about on wikipedia was that several open collector outputs can be tied together to one wire, implementing a sort of logic AND or logic OR configuration (depending on whether you're using positive-true or negative-true logic). Neither of these applications is relevant to me. Since the input pin of the controller to which I'm sending the opto switch signals is rated for 5-24 V, and the Vcc supply to the opto switch is meant to be 5 V, it seems to me that a totem pole output would be fine, and consumes less power overall (in general). My question is, I've never had to deal with either of these types of outputs before. Are there relative advantages or disadvantages that I've missed. Which type would you choose for this application?