September 5, 2008 6881076C25-E
2-4 General Overview: Control Head Assembly
2.4.9 Vehicle Interface Ports
The Vehicle Interface Ports (VIPs) allow the control head to activate external circuits and receive
inputs from the outside world. In general, VIP outputs are used for relay control and VIP inputs
accept inputs from external switches. See the cable kit section for typical connections of VIP input
switches and VIP output relays.
The VIP outputs are driven by logic within the control head for both the Dash and Remote Mount
configuration. Field programming of the radio can define the functions of these pins. The output
transistors that drive the VIP outputs can sink 300 mA of current. Primarily, they are used to control
external relays. These relays should be connected between the respective VIP output pin and
switched B+. Typical applications for VIP outputs are controlling the external horn/lights alarm and
activating the horn-ring transfer relay function.
Remote Mount Configuration:
The VIP pins are located on the back of the control head below the area labeled “VIP”. For Remote
Mount radios, all three VIP inputs and outputs are available at the rear of the control head. The VIP
inputs are connected to ground with either normally-open or normally-closed switches.
Dash Mount Configuration:
For the Dash Mount configuration, only two VIP output pins are available and they are located at the
15-pin accessory connector. VIP input lines are not available in this configuration.
2.4.10 Power Supplies
The +5-V supply is a three-terminal regulator IC to regulate the 12 V SWB+ down for the digital logic
hardware.
2.4.11 Ignition Sense Circuits
A transistor senses the vehicle ignition’s state, disabling the radio when the ignition is off. For
negative-ground systems, the orange lead is typically connected to the fuse box (+12 V).
NOTE: Refer to the ASTRO Spectra and Digital Spectra FM Two-Way Mobile Radios Installation
Manual (6881070C85) for more information on operating the radio independent of the ignition
switch.
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