Indicator flasher relay -VESPA 3-PIN 12V 10/21W AC- Vespa PK S, PK XL, PK XL2, PX EFL (1984-), Cosa, Cosa FL, T5 125cc, APE

It has 3 connections:

The current is alternately clocked on L1 and L2. Thus the alternate clocking of the front and rear turn signals is achieved. The sense behind it is to reduce the on-board load to a minimum so that the turn signals are still properly clocked even when idling (with little voltage from the alternator).

TIP: Due to the electronic control of the turn signal it is also perfectly suitable for handlebar end turn signals or similar. In contrast to a mechanically controlled relay (such as the round DC sheet metal relays of the old PX models), turn signals with less load (e.g. if only 10W bulbs are used) are then also clocked.
The turn signal switch is then simply connected to L1. L2 can, but does not have to, serve as an output for a flasher control lamp.

(US)