Sony WLL-CA55, Руководство по обслуживанию

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1-9 (E)
WLL-CA55
1-5-3. APR-69 Board
The APR board mainly comprises circuits for processing
audio signals and intercom signals. This board is also
equipped with an earphone circuit, a power supply circuit,
and a video signal circuit for return video and sync signal
generator lock.
Serial data transmitted from WLL-RX55 using the wireless
microphone system is processed by the IF board. Details of
these circuits are also described in this section.
Audio Signal
The audio circuit supports two channels, that is, AUDIO 1
and AUDIO 2.
For the AUDIO 1 channel, the circuit selects “CAM MIC”
signal from the camera, “SLOT-IN MIC” signal from the
wireless microphone system or “AUDIO 1” signal from
the XLR connector.
The menu of this unit specifies which input signal above is
transmitted to WLL-RX55. The specified input signal is
selected by the analog switches IC204 and IC205, and then
transferred to the microphone amplifier IC206.
The microphone connected to the XLR connector can be
supplied with
+
12 V or
+
48 V power. Power supply to the
microphone is possible, provided that the AUDIO 1 + 48V/
MIC/LINE switch by the XLR connector is set to “ + 48V”
and that either MIC POWER
+
12 V or
+
48 V is selected
by the menu. MIC POWER
+
48 V is selected by default.
The microphone amplifier gain is controlled by WLL-
RX55 while this unit is in communication with WLL-
RX55. In other cases, the gain control depends on the
menu setting. However, while the AUDIO 1
+
48V/MIC/
LINE switch is set to “LINE”, the gain is always _ 20 dB.
The signal amplified to approx. 220 mV by the micro-
phone amplifier is band-limited by the two-stage LPFs
with a 15 kHz cutoff frequency. The signal is then trans-
ferred to the VPR board and A/D converted, then sent to
the WLL-RX55 transmission process.
For the AUDIO 2 channel, no input selection circuit is
provided because only “AUDIO 2” signal from the XLR
connector is processed. Functions other than this are the
same as those for AUDIO 1.
n
The AUDIO 1 XLR connector is also used for input serial
digital data (multiplexed data of 700 protocol data, inter-
com signal and tally signal) transmitted from WLL-RX55.
For details, see “Serial Data from WLL-RX55”.
Intercom Signal
There are two types of intercom signal; one is from this
unit to WLL-RX55 and the other, vice versa.
The intercom system of WLL-CA55 greatly differs from
the conventional TRIAX system with respect to the
following points.
.
The signal band is 2 kHz for both directions.
. The signal from WLL-RX55 to this unit is digitally
compressed, which enables to transmit lesser volume of
intercom signal.
The intercom signal to WLL-RX55 passes through the 5-
pin INTERCOM connector to the intercom microphone
amplifier “INCOM TALK AMP” on the APR board. This
amplifier can be set so that it is applicable to three types of
microphones; carbon type, dynamic type and unbalanced
connection type. Further, its gain can be set for micro-
phones with various gains irrespective of microphone
types. These settings are available from the menu.
Amplified intercom signal is transferred through the 2 kHz
LPF to the DPR board as “INCOM TALK” signal. It is
then A/D converted and input to the “transmission to
WLL-RX55” process.
The intercom signal from WLL-RX55 is processed on the
IF board, and then sent to the APR board as serial digital
data “INCOM CCU DAT” (on the APR board “SDATA”).
n
Details of the processing of the intercom signal from
WLL-RX55 are described in “Serial Data from WLL-
RX55”.
The following processings are performed sequentially on
the APR board for the SDATA signal.
(1) D/A conversion
(2) Side-tone mixing
(3) Filtering with the 2 kHz LPF
(4) Level adjustment with the electronic variable resistor
IC409
Then, the signal is transferred to the INTERCOM connec-
tor (5-pin XLR) via the drive amplifier IC411.
To prevent noise from entering the signal when a communi-
cation error occurs during communication with WLL-RX55,
muting is performed by shifting the control signal level of
the electronic variable resistor to low level using the muting
signal from the IF board. Either the AUDIO CONT signal
from the camera or the MENU LVL IN signal from the
menu is used as the control signal for the electronic variable
resistor. The INTERCOM TALK ON/OFF/REMOTE
switch on the rear panel selects which one to use. When the
switch is set to “REMOTE”, the AUDIO CONT signal is
used. Otherwise, the MENU LVL IN signal is used.