GatesAir PT-353, Инструкция по установке и эксплуатации, Страница: 12 / 55

PT/PR-353 Program Audio Module Installation & Operation Manual 2 – Functional Description
Version 1.1
2-2 GatesAir
Intraplex Products
A green SRVC (service) indicator light stays on when the PT-353 module is powered and operating. A
red FAIL light indicates a hardware failure (DSP or logic circuitry malfunction). The SRVC indicator
light flashes on and off if a configuration error is present.
2.4 PR-353 Receiver
Input from the selected time slots of the receive bus (the RX-B bus to receive from a terminal or DI-A
port; the RX-A bus to receive from the DI-B port of a drop/insert multiplexer) is fed via the backplane
to the module.
The incoming signal passes to a DSP that provides several functions:
●
Turns on a green light to indicate input activity.
● Controls a bank of five peak-responding input level indicator lights, calibrated the same as those
on the PT-353 module. The red overload indicator light turns on at the maximum permissible
digital level of 0 dBFS (+24 dBm nominally).
● Manages FEC (forward error correction) process in the FPGA and corrects errors due to
transmission errors (.Section 2.7 – Reed-Solomon Forward Error Correction).
The resulting bitstream passes to the D/A converter and the analog outputs of the converter go to an
output level control and to a switchable circuit that provides de-emphasis in accordance with the ITU-T
Recommendation J.17 de-emphasis curve. De-emphasis must be used when the audio signal was pre-
emphasized on the input side and cannot be used when the audio was not pre-emphasized.
The audio then goes to the output amplifiers, which produce a balanced two-channel audio output with
a maximum signal level up to +24 dBu, referenced to 0.775 V. The output level from digital full scale
is adjustable from +9 dBu to +24 dBu, normally set at the factory to +20 dBu. Equipment jacks are
provided for test signal retrieval. The output impedance is 50 ohms. The resulting bitstream is also
applied to an AES/EBU transmitter IC that services the digital output (which is simultaneously active
with the analog output). If there is no external sync reference, the digital output uses the sample rate
of the transported audio. If there is a word clock source or a reference AES signal connected, a sample
rate converter is engaged, permitting the digital output to present the digital audio at the sample rate
of the local reference.
A green SRVC (service) indicator light stays on when the PR-353 module is powered and operating.
The SRVC indicator light blinks if a configuration error is present. A red FAIL indicator light indicates a
hardware failure (DSP or logic circuitry malfunction).
2.5 Alerts and Alarms
Alarm status is displayed in two different ways. The first way is by a local set of contacts on the MA-
508 and MA-509 module adapters or the MA-558 and MA-559 module adapters. Without power, these
contacts are closed. In normal operating mode, these contacts are held open. If there is a board or
power failure, the contacts are no longer held open; they close, creating an alarm condition.
Alarms are also displayed by the power supply. In the case of a minor or major failure, the yellow or
red indicator light turns on. Both the PT-353 and PR-353 modules can generate these alarms and
alerts:
●
Configuration errors cause the SRVC indicator light to flash, and the MA-508 and MA-509 contacts
close, creating an alarm condition. The yellow indicator light on the power supply also turns on.
Note: If service to the module is shut off by setting the OFF switch DOWN (SW3 on the PT-353
module and SW4 on the PR-353 module), the contacts on the module adapter are not active
and an alarm is not triggered.
● If software fails to reset the watchdog timer in an adequate amount of time, a board failure occurs
after three seconds and the red FAIL indicator turns on. If the board recovers, the FAIL indicator
light turns off after 10 seconds of valid operation. Additionally, if the FAIL light turns on, the
contact on the module adapter closes and the red indicator light on the power supply turns on.