TM9100 Installation Guide Installing the Radio 19© Tait Electronics Limited August 20052.5 Connecting the Power Cable to the Power SourceThis section provides information on connecting the power cable to thepower source.Power Connector The power connector is the interface to the vehicle battery and an optionalexternal remote speaker. Connecting a remote speaker is described in“Connecting a Remote Speaker” on page 21.Important This radio is designed to operate from a nominal 12Vnegative ground supply and may draw up to 15A of current.The radio will tolerate a supply voltage range of 10.8V to16.0V at the radio.Selecting the PowerSourceIn passenger vehicles, the radio is always connected directly to the batteryusing the power cable provided.In trucks, where direct connection to the battery is often not possible, theradio can be connected to a suitable terminal inside the fuse box that isconnected directly to the battery.24V-to-12VConverter In vehicles with a supply voltage larger than 16.0V, such as many trucks, itis essential to provide a suitably rated 24V-to-12V converter. This willisolate the radio from excessive battery voltage and provide the correct DCoperating conditions. Note that most 24V-to-12V converters already fittedare not rated sufficiently.Standby Current When connecting the radio to the battery without using the ignition signalas described on page 23, the standby current is approximately 50mA.When using the ignition signal to turn off the radio, the standby current isreduced to <3mA.Tip To reduce the standby current from 50mA to <3 mA without usingthe ignition signal, connect pin 4 (AUX GPI3) and pin 15 (GND)of the auxiliary connector.Table 2.1 Power connector (radio)—pins and signalsPinout Pin Signal name Description Signal type1 AGND Earth return for radio body power source Ground2 SPK– External speaker output. Balanced loadconfigurationAnalog3 SPK+ External speaker output. Balanced loadconfigurationAnalog4 13V8 BATT DC power input for radio body andcontrol headPowerrear view40W/50W radio1 2 3 4rear view25W radio