that provides an equal number of ones and zeros (a DC-balanced signal)
For signals with good DC-balancing, the useful spectral content of the data usually has a low frequency cutoff,
and it is possible to pass the information with minimal degradation in content. However, for any signal
passed through an AC-coupling circuit, you should expect a small portion of the signal to be filtered out.
Another possible meaning ... An analog circuit with good DC balance will maintain stable DC performance (avoiding drift or offset) despite changes in temperature, power supply voltage, operating mode, etc.