Lots of questions about how this wireless stuff actually works.
Lets jump right in:
I'm focusing on the invalid touches here, epee only.
With wired epee systems, the two wires of fencer A's epee are at some DC
voltage. By touching the bell guard of fencer B's epee, a circuit is closed
between the scoring box (battery + and sensor) through the two wires of
fencer A, tip contact, bell guard of B, ground wire of B, back to the
score box (battery -).
The current flowing makes the sensor detect an invalid hit.
Now cut the ground wire of B and the two wires of A.
Or, all of them while you're at it. Doesn't get better anyway.
So DC doesn't work any more, how about AC? Radio frequencies (RF)
can fly through the air with the greatest of ease. For a connection
you would need a transmitter, the air and a receiver. No ground needed.
But then, regular RF in the radio frequency bands should not be used, because
of the interference with other radio services.
But how about the frequency range between DC and the lowest frequency
used for radio transmission? No complaints there.
This signal doesn't fly as easily through the air as a RF signal.
So it is not transmitted without any wire or ground. We would need
a little bit of help, maybe a wire on one side but no need for a ground return.
(I hope I don't sound too ridiculous at this point- if you are versed in radio
frequency engineering, why didn't you post yourself, huh?)
The transmitter strength and the receiver sensitivity can be adjusted
such, that only a metallic contact between them makes the sensor go
off and indicate a invalid touch. No ground return.
So the transmitter would be on the back of fencer A, the signal goes through the body cord,
the tip, the bell guard of B, the ground wire of the body cord to the receiver.
That's one principle of how to get rid of the reels and floor cords.
On top of that there is a circuit in fencer A's box that checks with a DC circuit
for the closed tip switch.
So if only the tip switch is sensed - valid touch.
Tip switch detected plus receiver on fencer B goes of - invalid touch.
The tip switch sensed on A and the invalid detection from B is transmitted
by wireless modem (real RF this time) to the base station. In order to
address the standard scoring machine, the "wire" signals are recreated
by the RF receiver with transistor switches - like a short between
the two touch wires and a contact to the ground wire of fencer B.
Everything is needed twice for symmetry and different frequencies for "invalid" detection
are used to sort out the own transmitted frequency from the own receiver frequency.
OK, I'll stop here, hope it isn't too confusing.
Linear Mode
