[DOC] Add basic requirements

README.md

@@ -1,2 +1,40 @@
-# c3lingo-interpreter-unit
+# Conference Interpreter Unit
+[c3lingo.org](https://c3lingo.org) is doing the great job of translating many talks of the Chaos Communication Congress and other CCC-related events to multiple languages.
+But the required hardware for simultaneous translation is quite expensive to rent, even if it's "just" a specialized analog audio mixer.
 
+So the idea was born to design an easy to use hardware with the special requirements of our interpreters in mind.
+
+
+## Requirements
+The hardware unit should deliver the native audio (stage/ hall mix) to the interpreter's headset and provide a sum of all interpreter's microphone to the input of the video streaming/ recording chain.
+Mixing of the final translated audio (ducking the native audio with the translation) will be done as part of the streaming/ recording chain, so the interpreter unit should just provide the sum of all microphones.
+
+Normally just 2 interpreters will provide one translation, but demanding talks might require 3 people.
+So either 3 headphone inputs/ outputs should be provided or it must be possible to daisy-chain multiple units.
+
+The user interface of the unit should be as simple, as possible to decrease the risk of mis-configuration.
+This means, that no compressor and equalizer will be added in the input group.
+
+General requirements:
+- Line input of stage/ hall mix (native language) (XLR/ 6.3 mm balanced jack combo connector)
+- 3x Microphone input (XLR) (at first just dynamic microphones)
+    * VU-Meter for each input channel. (Perhaps with special color scheme: too quiet, good, too loud, clipping)
+    * Fader/ Potentiometer for gain control
+    * Mute switch (on/ off position, with state LED)
+    * Temporary mute button (momentary switch)
+- 3x Headphone output (6.3 mm mono/ stereo (2x mono) jack)
+    * Should output mix of native audio and own microphone
+    * Potentiometer for output volume
+    * Potentiometer for volume of own microphone in the mix
+- Outputs:
+    * Sum of all translators (XLR/ 6.3 mm balanced jack combo connector)
+
+All inputs (besides the microphones) and outputs should:
+- expect/ deliver a nominal level of +6dBu (german TV broadcast standard, 0 dBu = 0,775 Veff)
+- be transformer balanced and galvanically isolated
+
+
+## Status
+Requirements collection done, first research for circuit design, but no real progress yet.
+
+Help is always appreciated!