Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

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Principle of Operation

Principle of Operation
In the US version, the Telematic Control Unit has an NAD (Network Access Device) that works in the AMPS/COMA standard with the frequencies 800/1900 MHz. The TCU features a handsfree system with full duplex transmission. This makes it possible to speak and listen simultaneously. The position of the vehicle is determined by the TCU by means of a built in GPS receiver. In the event of a crash, the TCU sends an SMS with this location data to the provider. Furthermore, the TCU has an interface for the connection of an emergency call button (E/B Call). The emergency call button is a dual function switch with two keys: one for the emergency call and one for the breakdown call. The emergency call button is standard equipment.