The Signature series allows the possibility to operate with two different band widths in the same deployment when using concurrent or alternating plans. To remove any confusion we use the term long range mode instead of narrowband since single ping standard deviation is still lower than our classic narrowband instruments (e.g. AquaPro or AWAC).

In the Deployment software there is a field called "Long Range Mode" which can be seen in the Effect tab on the right of the Deployment Wizard. Long range mode ON means that the bandwidth is reduced to get increased range, whereas OFF means that broadband is used. The two modes differ mainly in terms of power consumption, accuracy and range. Burst mode will always use broadband. Current profile/Average mode will turn on Long range mode when it detects that the desired max range will not be reached using broadband with the selected configuration (dependent on power level, range and cell size). For example, the Signature500 at max power level = 0dB and cell size = 1m will turn on Long range mode when the desired range is between 49m and 50m. 

Note that the center frequency is still the same (for example 500 kHz for a Signature500) both with and without Long range mode activated. The only difference is the bandwidth around the center frequency. For broadband measurements the bandwidth is 25%, while with long range mode activated the bandwidth is reduced to 6%.

The Signature55 is slightly different since it can operate in Coarse (Long range mode) or Fine profile (full bandwidth) which uses two different center frequencies. In Coarse mode it will use a narrower bandwidth (6%) with center frequency of 55kHz which gives the longest range, sacrificing some resolution. In the Fine profile a broadband ping (with bandwidth 25%) centered around 75kHz will be used which gives high resolution, but sacrificing some range.