Hi Everyone,
I am new to this current loop concept and was wonder if this
old/archiac config 4-20mA Current Loop is used only to pass analog signals
between 4 and 20 mA or the two ends of the range can be used as digital
signal signifying binary 0(4mA) and 1(20 mA).
Certainly you can use a current loop to transmit a two-level analog signal level and interpret it as two digital states. But it's overkill if that's all you are using the current loop for.
Analog current loop isn't archaic, it's very functional for a wide range of industrial applications. Digital current loop is still used in some applications, e.g. for MIDI (music instrument digital interface). For an overview https://en.wikipedia.org/wiki/Current_loop