I have the opportunity to buy an old LZX Flip Flop but I don’t know what it does. Can someone please to me what a Flip Flop does as I think there is one in the Castle series as well? Any images would be great of its output. Thanks group 
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A flip-flop is a one bit memory cell. When the CLOCK input receives a rising edge (a 0V to 1V transition), it will capture the current digital state of the input. It will hold the captured value on its output until another clock edge is received, at which point it will sample the input again. Many flip-flops also have a RESET input allowing you to clear the stored value so that the output becomes low again.
By the “digital state” of the input signal, I mean that its only possible output values are “high” corresponding to a “high” input (in LZX land, a high output will be 1V. an input will be high if it is at least 0.5V.) or “low” (0V, or less than 0.5V) – the actual analog value of the input signal is only compared to see if it is at least “halfway on”. A flip-flop is sort of like a sample-and-hold except that it will only output 0V or 1V, not any analog values in between.
Example usage of the Castle flip flop in a patch:
Castle Patching 002: Digital Sample and Hold
You may be able to find more examples by searching this forum for flip-flop.
More details about implementation and applications: Flip-flop (electronics) - Wikipedia
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Oh cool! So almost like a sample and hold in Eurorack. Thank you so much. I think I’ll get this.
From the Archives:
video flip flops is a high speed digital logic processing module with four single bit digital memory functions. it is capable of processing signals throughout the video bandwidth. each of the ten inputs includes a high speed comparator which converts any input signal into key logic around a threshold of 0.5 volts. as with all modules in the lzx visionary line, the inputs can therefore receive any type of signal - not just binary logic pulses.
there are two identical channels arranged in columns. each column contains two flip flops. the first flipflop is a toggle flipflop with toggle, set, and reset inputs. a positive pulse on the set input will switch the output high. a positive pulse on the reset input will switch the output low. a positive pulse (or button press) on the toggle input will invert the current value of the output. below the toggle flipflop is a data flipflop. the data flipflop will transfer the value of the data input to the output, whenever a positive pulse is received at the clock input jack.
the toggle flipflop is very useful for complex shape processing and combinations of key signals. the data flip flop is useful for quantization of input data, forcing the input to only update in time with the secondary clock signal.
please note: this module requires connection to the video sync generator by means of a video sync distribution chain cable which must be purchased separately.
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Here’s a link to another thread where Jim. Here in Berlin created some videos that are good examples of what the Castle 111 Flip-Flops does.
There is an issue regarding the Castle module, a cut in the PCB has to be made & a connecting wire soldered, its documented on here somewhere. Maybe the one you’ve been offered @Fallinggirl has been correctly modified.
The issue is only present on Castle Flip Flops RevC
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For anyone wondering, here’s the URL:
I’ll also attach a screenshot of the page to include the instructions but here’s the image file.
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Thanks so much for the heads up