Today in my email, a question about the need to use a resistor in a discriminator output. My reply:
Is safe sex necessary?
https://www.discriminator.nl/faq/index-en.html - 'Discriminator Outputs', Question 6 -
'What's the function of the resistor?
Connecting or disconnecting an interface to the discriminator output might cause a short-circuit. The limiting resistor prevents the discriminator IC from being loaded or damaged. Further to that, it prevents your PC's microphone or line input from being overloaded.'