Pulses and chips and...
Salute!
Murphy is getting to where I was intending.
The pulse length of approx 10 msec means that we have plenty of time chips ( the bits that Murphy describes) to encode the pulse. Same as the GPS encoding system that allows numerous satellites to transmit on the same freq. So we can transmit 3750 chips per pulse. If we only transmit once per second, then we can get by with very low power requirements on the part of the transmitter.
We know the base frequency and can scan back and forth until we get a distinct correlation if we know the "code". The signal can picked outta noise at really low S/N rations.
So why not specific codes for specific pingers?
Further, using only a few chips of the transmitted ping, we have a few thousand chips left over to transmit stuff like last known position and other stuff.
Gums sends....
PS, As with Murphy, I had to learn about GPS signal processing in order to develop our latest guided weapons and the aircraft interfaces and other stuff. For ground surveys we actually locked on to the base frequency of the satellites and with a phase resolver could get centimeter or even millimeter accuracy.