rednet senderID

hello miner

first i must say sorry for my terrible english, i hope i can explain you what i need.

i don´t understand how i can give a computer a senderID or receiverID.

my first computer the sender do this :

rednet.open("top")
rednet.send(id01, "redstoneOn")

then i have two other computers - i want that one computer is id01 and the other id02.
when i give the signal from computer sender, i want that only the computer with id01 get the signal.
i have write for the receiver one prog and copy it to the other receiver and change only the second line id01 to id02.

receiver01:

rednet.open("top")
id01, a = rednet.receive()
if a == "redstoneOn" then
rs.setOutput("left", true)
end

receiver02:

rednet.open("top")
id02, a = rednet.receive()
if a == "redstoneOn" then
rs.setOutput("left", true)
end

i start both receiver (the second will later get a other signal from an other computer, but first i need diffrent signals)
and then i start the sender and both receiver get a signal, but why. i have think i can do : rednet.send( <— and here is the id from sender
and id01, a = rednet.receive() - i have think the beginning of this line i say this is the receiverID.

my end finish is, i have a nucular station and want give my eight reactors over wireless a signal to go on or off.for this i have eight computers to send and
eight computer to receive. better one computer sender and eight computer receiver. i want say reactor 1 &amp; 2 on , 3 off, 4 on, …

so i hope you understand my problem with the sender- &amp; receiverID´s.

if you open a computer and type 'id' it will return the ID. then you type that in the ID place of a rednet message

this it - i don´t need more
many thx+#