Shure UC2 Hand-Held UHF Transmitter
Characteristics
7
25A1044 (RI)
Any switch change is comprised of state toggle from odd to even,
and vice versa. Only this change is detected, and it is followed by a
multiplexed switch read, in which U303, pins 7 and 8, become selectively
grounded outputs to read the selected switch’s state on pins 3 through 6.
A multiplexed switch read is preceded by tone key and rf mutes.
This mutes the audio in the receiver to allow a quiet change to another
frequency.
For JA frequencies, the Group switch has 16 positions, and the
Channel switch has 10 positions.
Power Switch and Mute Interface
When a transmitter is turned off, the
PWRDN
signal goes to logic low
on U303, pin 19. This immediately disables the tone key, and the power
hold circuit automatically kicks in to bypass the power switch. This is
followed by 500 mS of delay, and then the rf is muted and turned off.
The power hold circuit is also disabled at this point, and the transmitter
shuts off.
