We have to make a two tone siren using a Schmitt Trigger (74HC14N) and my group and I came up with this circuit. Pretty simple really, but the tutor for our class said that it's not a very good design because: it's not a good idea to drive the two Schmitt Triggers at the same time, and because of the position of the diode, we'd have a high output impedance right after it, along with the low output impedance coming out of the top Schmitt Trigger. He mentioned that we'd have to justify in our report that these values meet the specs of the IC, since we could damage it, or other components. Just wondering if someone could provide a more clear explanation since I don't exactly understand just why/how our circuit composition could lead to a damaged component, or why it isn't a good idea to drive the two triggers at the same time? This is the circuit (power is given to the IC through a 3V battery): It produces the two tones (similar to an ambulance siren) btw. But that's also another thing that we're unsure of, just how it produces them. We understand that the configuration we have gives rise to a square wave, and we decided to allow the square wave of the top Schmitt Trigger to pass through (during which the capacitor is discharging, right?) and then the diode kicks in by allowing current to pass through from the bottom trigger (thus allowing the the top capacitor to charge, with the bottom one discharging) and thus allowing that tone to go through. Is this a correct interpretation? (Btw, he said that to reduce these effects, we should just introduce a resistor before the diode) Thanks.