Crude Powerline FSK comms literally shorts the power bus at a certain frequency?

[cupoftea]

Hi,
Is there such thing as a powerline FSK comms system where multiple points along a long cable (bus) are
supplied power by the cable, but also the cable is literally shorted/opened at a certain frequency so as to give an
FSK powerline comms system? All the load circuitry doesn't get affected by the bus getting shorted because the loads
are supplied by capacitor banks which are downstream of high resistances connected to the bus so that the capacitor bank is
effectively "isolated" from the bus.
Obviously there just needs to be some initiation time so that the capacitors can get charged up at power up time.

 

[dick_freebird]

Powerline comms are short haul from what I've seen.
You throw C-blocked HF carrier onto the (effectively)
long-wire-L-blocked 50/60Hz line and you pick it
off C-blocked, elsewhere (before it's attenuated too
badly by L / distance).

So "AC short" (but at an AC frequency well
out-of-band). Since a useful modern data rate
is > MBPS carrier will be way up there, C will be
small, "short" will escape notice (just more
small signal noise, picocoulomb blips)

 

[cupoftea]

Thanks, i see what you mean , you are thinking of coupling the signal to the powerline via a blocking capacitor. I have seen that before too. Also, AYK, you get transformer coupling. However, the schem i have in fornt of me has none of that...it just has a BCX56 SOT89 NPN shorting the rail.....(24v rail)...well, its not shorting as its got a 75R in series with it.
But i guess due to the powerline L, that will give a bit of a dip in the rail which will be detected by the detector?
Have you seen that type of FSK system before?

I cannot see any blocking cap or signal transformer here.
The schem i have is on multiple pages with cross references going off all over the place but i deffo dont see any C or Transformer.