The idea is to build a box that has control over the four buttons typically
found at the top of an MC45 type hand mike.
These are the PF key, vfo, call and MR.
RE assignable on most radios to perform various functions.
If a person uses a desk mike with either the kenwood dual band mobile rigs,
or any of the HF rigs that offer both S meter and freq read out, then the
operator  is limited to the use of a single function key, the one on the
radio.
This means you must assign either the freq readout, or S meter read out to
that single PF key, not allowing for both to be simaltaniously programmed.
This is only if you use a desk mike, or a microphone that does not have the
four function keys.
this is how these functions are performed electronically using 3 pins of the
mike jack:
This is a listing for the mc45DM mikes, but I would suspect that the
resister values are universal for most kenwood radios.
This  shows the pinout for an RJ45, not an 8 pin kenwood din jack like on
the ts2000.
The pinout for the ts2000 would likely be something like pin 3 and pin four
shorter to either pin 6, or pin 8, which is PTT or chassis ground.


Resistance value
between pin 6 and pin 8
between pin 6 and pin 1
0 ohm
UP
DWN
22 kohm
CALL
MR
100 kohm
VFO
PF

Personally, I very rarely use more then two function keys on my mc45DM and
the ts2000.  I use two of the keys for S meter reading and freq readout.
So, for me, I would simply reassign the VFO key for freq read out, and the
PF key for S meter readout in the rigs menus, and then use a 100K ohm
resister on a two way mini momentary toggles switch, or some other sort of
microswitch with a two way momentary set up.  Basically you short pin 8 to
pin 6 through a 100K resister to obtain the VFO function switch, and short
pin 1 to pin 6 through a 100K resister to obtain the PF keys function.
I suspect that pin 6 is chassis ground, but perhaps not since there is one
more pin for a typical 8 pin round jack settup that doesn't appear to have a
function, which might be that of controlling the function keys.

A small hamond box, with an 8 pin standard din jack, or perhaps with the
RJ45, one for input, one for out put, would fit the bill just nicely.
Now, how to implement a DTMF pad hmmmm.
While I'm at it, I might as well put in an XLR jack  for a studio
microphone, a PTT switch, and a jack for a foot switch.
But of course, that would mean a relay, and an audio isolation transformer.

any thoughts are welcome on what I have outlined here.

73
Colin, V A6BKX