Sparco GSM Car To Pit Intercom is a simple and cost effective way to communicate clearly from pit to car via this sim card driven GSM device. The unit is 12v powered (lead included) and is controlled by a simple on/off volume switch. It features a nexus male plug and can be adapted to suit most helmet headsets with either adaptor leads or female to female extension leads.
It also comes with an antenna with multi surface mounting. As long as there’s a mobile reception with the SIM provider in the area, it works in a similar way to a mobile phone.