According to the Husqvarna patent, the signal should be 40 Volt peak-to-peak, each group of pulses is repeated at approx 80 Hz, the leading pulse is 100 microseconds and the following data pulses are 50 microseconds. The output stage in the charging station is a push-pull stage driving the pulses 20 volts in one direction and then 20 volts in the opposite polarity, creating balances pulses at 40 volts peak-to-peak.
Acc to the patent the maximum pulse current is about 2 amps.
Then of course the patent is wide enough to accomodate similar solutions, so the values I have given are not necessarily those used in practice. However, because people can trace the signal with an old AM radio, the pulses would have quite a lot of overtones which indicate short pulses as described in the paten.
Unfortunately I have given away my old oscilloscope years ago, otherwise I would be lying in the grass analysing the signal....