MM-010019-001, Rev. B
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8
RADIO DC POWER INSTALLATION
Refer to the wiring diagram at the end of this manual as necessary when performing wiring procedures
presented in this section. With regards to control head installation, power connections for the CH-721
Scan and CH-721 System control heads are exactly the same.
8.1 ON/OFF POWER WIRING CONFIGURATIONS
The mobile radio can be wired in a motor vehicle in various ways to accommodate the user’s preferences.
In all cases, its red power wire must be connected through an in-line fuse to raw battery power (positive
battery terminal). The white ignition wire of the radio’s DC Power Cable is only used for the data-only
radio (i.e., no control head), and it is the only means for turning its power on. An in-line switch for
switched battery power to the radio must not be considered unless the user has the discipline to turn off
the radio through the control head’s on/off/volume control or through a separate switch wired to the
ignition sense wire. Failure to wait for the radio to completely power down before disconnecting battery
power will not damage the radio; however, it may result in the loss of settings that have changed (e.g.,
volume setting, etc.) during the operating session.
On/Off power functions for the radio are controlled by the control head or, in the case of a Data-Only
radio, within the radio itself. The following power wiring configurations are supported:
•
Radio turns on/off automatically with vehicle’s ignition switch/key
— The white sense wire of the
control head’s (or data-only radio’s) DC Power Cable is connected to a fused switched power source,
typically identified as “Accessory” power. This source must switch on (up to positive (+) battery
voltage potential) when the vehicle’s ignition switch/key turns on, and it must switch off (to near zero
volts) when the ignition switch/key turns off. The required fuse rating is 2 amperes. An ATM fuse
holder and fuse are included with the applicable fuse kit. When using this configuration, the CH-721
control head’s on/off/volume control must be left in the on position for automatic power-up/down to
function properly.
•
Radio turns on with a manual switch
— The white sense wire of the control head’s (or data-only
radio’s) DC Power Cable is connected to one side of a manual toggle switch and the other side of this
switch is connected to a fused vehicle power source. This configuration is used when, for example,
the radio must remain on even when the ignition key must be removed from the vehicle and a
separate on/off switch is acceptable. The required fuse rating is 2 amperes if no other devices share
the switch. If other devices share the switch, the 2-ampere ATM fuse must be spliced in the white
wire on the load/switched power side of the switch. When using this configuration, the CH-721
control head’s on/off/volume control must be left in the on position for automatic power-up/down to
function properly.
•
Radio turns on with control head’s on/off/volume control (“hot wired”)
— This configuration
allows radio power on/off control only via the control head’s on/off/volume control. It may be desired
if, for example, the radio must remain on even when the ignition key must be removed from the
vehicle and a separate on/off switch is not desired. In this case, the white sense wire of the control
head’s DC Power Cable must be connected to unswitched and fused vehicle power. The required fuse
rating is 2 amperes.
8.2 POWER INSTALLATION PROCEDURE
8.2.1
Install Main Fuse Holder and 10-AWG Red Wire
The main power fuse, its holder, and related items are included in Fuse Distribution Rail Kit FS23057
illustrated in Figure 8-1 on page 32. Follow the procedure in this section to wire fused main power from
