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For the same logic family, 74LS in this case, tie an output directly to an input. It doesn't matter what the logic function is, output ties directly to input. For the 74LS family, one output can drive …

The manual does not give absolute input limits, so there is no way to tell if 8 volts will kill it. As a result, you should assume that it will. And be careful how you reduce the voltage. Simply using …

Because the 2003 has Darlington outputs, and your optocoupler current is presumably in the range of ~10 mA, you should count on an output voltage of about a volt, maybe a bit less. Note from the data …

Using standard TTL to drive 50 ohms is a problem which goes way back. I'd advise making a little box to go between the NI and TCSPC which uses a MOSFET driver and run it off 5 volts. …

This doesn't actually work very well, given the limitations of the topology, and TTL gates had much lower ability to source current than to sink it. …

What you want is a digital multiplexer, in this case a 74LS157. The following schematic should give you an idea of how it would work. This would take 3/4 of a single chip. simulate this circuit …

This is very simple. You'll need a 74LS00, a DPST switch, and two resistors. The circuit looks like simulate this circuit – Schematic created using CircuitLab

A TTL gate which is not being abused will output either less than 0.4 volts or more than 2.6 volts. But this is only half the story. … TTL is only guaranteed to operate correctly for inputs of less than 0.8 volts or more than 2.0 volts. …

Additionally, the TTL/LSTTL/ALSTTL/FAST/etc families are pretty much restricted to 4 bit logic functions (including ALUs) and 8 bit storage/bus functions. 16 bit functions never were much available, in …

I am assuming that you do not have an oscilloscope, and are looking for visible indicators of oscillation. If I'm wrong, you can ignore the following. The answer is (I suspect) pretty simple: in both …

Please read https://learn.adafruit.com/adafruit-neopixel-uberguide/best-practices If you've already read it, read it again and do what it says this time. You are violating best practices in at least …

A number of tips about dealing with (LS)TTL: 1) Inputs should be either grounded or pulled high with a 1k pullup resistor. 2) Output LEDs should be connected to +5 with a 1k pullup resistor. … You've missed the part in the Youtube video where it is pointed out that TTL inputs float high if no connection is made, so your circuit really ought to be turning on ALL the LEDs, not just the 2 that …

B19 on the PC104 does no such thing. It is RFSH*, and is used as part of a refresh cycle for dynamic RAM. You need a decoder for A4 - A7 to do what you want. A 373 will do exactly the opposite of wha …

That you want to "square out" your oscillator suggests that it is not providing a logic-level signal, but rather something like a sine wave. Such a sine wave is, of course, referenced to zero, so the …

If your schematic is correct, your problem is that you're letting the R input float. With 7400 chips, a floating input functions as a logical 1. As a result, immediately after your set pulse occurs (a …