 Identification for each individual transmitter needed to be embedded in the signal for troubleshooting purposes, yet the main data stream on every synchronised transmitter must be identical; this is done by adding a second, low bit rate spread spectrum signal 27–30 dB weaker than the main signal.As this "watermark" identifier is buried under the stronger main signal, multiple repetitions of this same identifier could be received and summed in order to provide a readable version of the watermark to broadcast technicians.A standard receiver, meanwhile, would see the same signal from all transmitters by design.