7.1.2 Function 2 (F2)Press the HORN / 2 key on the numeric keypad. F2 is labeled with a whistleicon to remind you that this is the preferred function for whistle or horn operation.F2 is a special non-latching function. This means that F2 can be used to controla whistle or horn sound from the decoder. It will only sound when F2 isbeing held down. This lets you vary the length of time that the whistle blows,just like the prototype.