Shure U4D Service Manual page 7

User Interface Section
Audio Output Level Control R110
RSSI Bar Graph Section
Audiometer Bar Graph Section
Diversity LEDs D101 and D102
Digital to Analog Converter Section
25D1062 (AG)
Shure U4D Dual Diversity UHF Receiver
The user interface section consists of switches SW101 MENU,
SW103 SELECT, SW102 UP (+), and SW104 DOWN (–). These
switches provide access to various user-programmable menus on the
front panel display. The LCD provides the user with feedback for all
switch actions performed.
The audio output level control potentiometer has no associated
circuitry in this section. Refer to the Audio Section.
Channel A
Bar graph driver U104 gets the DRSSI_CH_A analog signal (U104.5,
P102.6, I155) from the rf-audio board and indicates its strength on the
5-LED bar graph formed by D117, D115, D110, D109, and D105.
Channel B
Bar graph driver U102 gets the DRSSI_CH_B analog signal (U102.5,
P102.11, I170) from the rf-audio board and indicates its strength on the
5-LED bar graph formed by D116, D114, D111, D108, and D106.
Bar graph driver U105 gets the DAUDMTR audio metering (averag-
ing only, no peak) signal (U105.5, P102.13, I156) from the rf-audio board
and indicates its strength on the 7-LED bar graph formed by D119, D118,
D113, D112, D107, D104, and D103.
Diversity LEDs A and B have no associated circuitry in this section.
Refer to the Audio Section.
The microcontroller communicates with 8-bit serial D/A converter
U215 over two signal wires, DSQUELCH (P102.3, U103.10, TP113) and
DSCL (P102.15, U103.9, T114), to set up the audio squelch threshold.
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Circuit Description