> So I want to have about 3 LEDs to light and extinguish in sequence
> with the flashing equipment lights.  Also I want the transmission/
> sensing circuit to be minimally invasive

"Minimally invasive" in what sense ? Aesthetically (eg an LDR stuck
on the outside of the light) or electrically ? Taking a tap from the bulb
supply voltage isn't going to be that invasive, and the circuit can be
made very small

> On the equipment I have 12V available and could make a voltage
> divider for necessary voltages.  
> 
> When the lights on equipment are no longer flashing I want the
> transmitter/receivers to go to sleep if possible to conserve energy

The simplest way to do this would be to power the transmitter
with one or two PIC pins. The PIC would normally be asleep
waiting for an INT trigger. For nW parts (like a 12F629 or 675)
the sleep current is just a few nA, so that will have little impact
on the voltage you're monitoring. INT wakes it up and it then
supplies Vcc to the transmitter. As you want to just echo a bulb
flashing I would suggest this ;

When the bulb turns on

- send a stream of 01, perhaps a couple of bytes worth, to settle
the AGC. These small receivers' AGCs are at full gain looking
for a signal and you get random noise from them with no signal.
You'll not get reliable data out of the receiver until the AGC has
properly recognised a legitimate transmission

- End the pre-amble with a marker. For a product I make, the
last byte of the pre-amble is 00FF, using a bit time of nominally
1ms. Both ends of the comms use a 12F with 4MHz IntRC. A
timer in the PIC detects that last FF and knows the next bits are
data. The receiver PIC uses this FF to also set the bit time of the
received data, as the frequency of IntRC is temperature and voltage
dependent, something I have to account for in a remote battery-
powered transmitter

- follow this pre-amble with a recognisable character, eg ASCII "1".
This is the signal to turn LED1 on. Any character will do, as long as
the receiver PIC is programmed to respond. Manchester encoding
is desirable, as it converts each bit of data to either 01 or 10, so there
are no long strings of 0 or 1 bits, which will allow the AGC output to
increase and make the data received noisy or "lumpy", which could
lead to errors

- for the other LEDs, use eg ASCII "2" and ASCII "3"

- Do the same when the bulb turns off, except send a "turn LED off"
signal. This could be the same, ASCII "1", or ASCII "0" for example

How you manage this the best way depends on the timing of the
bulb flashes and how long they flash for. And also whether there
would be simultaneous events. If there are, you would need to add
a fixed delay to individual transmissions so that there aren't data or
RF clashes in the air

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