To find the answer, we need to go back to the year 2011. I had recently re-homed myself here and was communicating with
asbokid. The
Bald_Eagle1 had landed with a very long tale of woe about his erratic VDSL2 (ITU-T G.993.2), profile 8a, service and
Walter was attempting to improve the Internet access for Ewhurstians, in Surrey.
I was given a Huawei HG612 and once it was unlocked, by carefully following the instructions provided by
asbokid, there was a mass of data that could only be understood by creating what has become known as the "snapshot plots". They are, of course, the Bit Loading, SNR, QLN and Hlog plots (all versus the sub-carrier index (or tone number)). The suggestion was to make use of GNUplot . . .
At that time all xDSL services made use of frequency division duplex (FDD), splitting the available bandwidth into upstream (US) and downstream (DS) bands. Back then, my initial proof-of-concept code was created as a Bourne again shell (bash) script which was then given to
Bald_Eagle1 to develop. The US and DS bands needed to be in different colours to aid the visualisation for each snapshot plot. And so to the question: "
Why did the kuro neko choose the colours green and red for the US and DS bands, respectively?"
I think it is quite common that if a person needs to think of colours, to label or otherwise mark some entities, the triplet "red, green and blue" will come to mind
in that order. Why that order? I have no idea. If we think about that short list of colours we can see that they are in order of decreasing wavelength and increasing frequency. Which is a good enough reason for that ordering. Another set of colours that easily comes to mind (at least for some of us) is "blue, orange, green, brown and slate (or grey)". Finally, there are the seven colours of the visible spectrum "red, orange, yellow, green, blue, indigo and violet".
It is well known that the
kuro neko wears a red collar and the reason for that colour collar is identical to the reason for
psychopomp1's choice of
avatar. But that still does not answer the question "
Why Green and Red?"
Let us think about a FDD xDSL circuit. It is just a pair of transceiver units at either end of a radio frequency transmission line. One transceiver is the DSLAM or MSAN, i.e. the xTU-C, and the other is the EU's CPE, i.e. the xTU-R. The labelling of the FDD bands, US and DS, is relative to the xTU-R. If it helps, the US band can be called the transmit band and the DS band can be called the receive band. Those with experience of the telephony transmission (core) network, repeater stations, four-wire circuits, etc, (be they either analogue or digital) may well refer to such as the Go circuit and the Return circuit. And so the initial question has been answered.
Perhaps the following two lines will clarify things --
US Transmit Go Green
DS Receive Return Red