Shure UC1L Service Manual page 5

Transmitter Display Board
25A1043 (RI)
The transmitter is unmuted by bringing the gate low (
During transmitter power
bringing the base of Q103 and Q105 high. When the rf is muted this
way, the carrier signal of the transmitter is not allowed to drift off
frequency during power
When the external mute switch is closed, the ring and sleeve on the
jack are connected, or the tip and sleeve can be connected, depending
on how the switch is wired.
If the tip is connected to the sleeve, this grounds the IRQ signal
line that is connected to the microprocessor. Then, the 33 kHz tone key
signal is muted (
TONEMUTE1
bringing the base of Q103 and Q104 high (
power is then turned off via the
the Vcc line to the VCO and the last rf amps.
If the ring is connected to the sleeve, this grounds the
The grounds Q4 at the output of the tone key oscillator circuit.
TKMUTE1
This mutes the audio signal immediately.
UHF Body-Pack Transmitter Digital Section
The digital section contains several circuitry blocks.
Microcontroller Section
The microcontroller section consists of a U101 microcontroller. The
rotary switches indicate the UHF frequency group and channel. A 4.000
MHz oscillator provides the operating frequency to the microcontroller.
The oscillator circuit includes C117, C118, and Y102. U103, R106, and
C120 form the reset circuit. U103 is the reset IC that resets the U101
microcontroller if the 5 Vdc normal operating voltage falls below 4.3 Vdc.
R115 and C119 form the power supply filter circuit.
Memory Section
The memory section consists of U102, a non-volatile Electrically
Erasable / Programmable Read Only Memory (
mapping of compatible groups and channels. The microcontroller serially
communicates with this part via data and clock lines to read the frequen-
cy corresponding to the group and channel position. Ability to write to
this memory occurs during factory programming only.
During normal usage, this memory is used as a look-up table only.
Additional detail about the contents of
ing sections.
R103 and R108 resistors allow the clock and data lines to be driven
independently of the microcontroller port pin states during in-circuit
programming of
EEPROM
5
Shure UC1 Body-Pack UHF Transmitter
conditions, the rf power is first muted by
OFF
or conditions.
ON OFF
). The transmitter rf power is muted by
RFMUTE1
signal. This is done by reducing
RFOFF1
EEPROM
is covered in the follow-
EEPROM
.
).
RFUNMUTE
). Finally, the rf
.
TKMUTE1
) that stores the
Characteristics