Manual Number 9018205 Revision F, April 1, 2021
15
4.3 USB OPERATION
For units with USB Charging Ports, there are single and dual Type A versions available as well as
the CH93MAX dual Type A/Type C version.
The Type A USB Charging Ports convert the specified DC input voltage range to a 5 VDC output.
Type C USB-PD (Power Delivery) Charging Ports convert the specified DC input voltage range
specified to either 5, 9, 15, or 20 VDC. Both types employ intelligent control and use voltage
signals to negotiate the maximum power (voltage and current) that each individual Personal
Electronic Device (PED) allows. This provides for the fastest charging speeds possible for all
devices including phones, tablets, and laptops. The output voltage and power is applied to the
USB-A ports in per the
USB Battery Charging 1.2 Compliance Plan
and the USB-C/PD ports in
accordance with
USB 3.1
and the
USB Power Delivery
standards, versions 2.0 and 3.0.
To ensure enhanced cybersecurity protocols, no data is transferred from the unit to the attached
device or from the device to the unit or aircraft systems. Only power and power negotiation signals
are exchanged between the CH93 and the device(s) being charged.
4.4 DIMMING FUNCTIONS
The brightness control on the CH93 can use fully automatic control or a combination of external
and automatic control. For fully automatic control, the internal photocell is used to adjust the
brightness from minimum to maximum brightness by sensing and responding to the current
ambient light conditions. For external control using a dimming bus adjustment, the brightness can
be manually controlled by supplying a lighting input voltage. The lighting input voltage will be
compared to the power input and will control the lighting when it is between 20-100% of the power
input. A voltage equal to the aircraft bus voltage (100%) corresponds to maximum brightness. If
the lighting voltage is less than 20% of the power input voltage (or off), dimming will be
automatically controlled by the ambient light sensed by the photocell built into the unit.
Display Dimming Adjustment (Type 1 units)
To adjust the brightness range of the clock on Type 1 units for optimal daytime and night-time
viewing, as well as balance amongst other panel instruments, use the two trimming
potentiometers (trim pot) adjustments on the rear of the unit as shown in Figure 3.1. Set the
input voltage/lighting bus to maximum and turn the “Aircraft Dim Adjust” screw to raise or
lower the brightness. Next, turn the input voltage/lighting bus off in completely dark conditions
and turn the “Photocell Dim Adjust” screw to raise or lower the brightness.
NOTE
: For Type 1 units, the adjustment screw has a single 360° range of rotation.
Exceeding its limits past the stops will damage the unit. Adjust lightly.
CAUTION
