Specifications
Functional Description and Theory of Operation
PT/PR-150C Module Installation & Operation Manual
Harris Corporation
Issue 1, October 2000
Intraplex Products
5-6
5.3.2
PR-150C Receiver
Figure 5-2 shows a simplified block diagram of the PR-150C receiver.
Input from the selected time slot(s) is picked off the backplane and fed to a DSP
containing the apt-X decoder for expansion of the signal. Green ACTIVITY
(ACT) indicators for each channel light to show the presence of a valid input
signal (neither all zeroes nor all ones).
If the module is set to operate in 15-bit mode, the 16th bit is checked to verify that
it is a 1; if it is not, the sample is errored and the green SERVICE (SRVC)
indicator flashes.
The expanded receive data stream then passes to the D/A converter, and the
analog outputs of the converter pass through a lowpass filter, then goes to a
switchable circuit that provides de-emphasis in accordance with ITU-T
Recommendation J.17. De-emphasis must be used when the audio signal was
pre-emphasized on the input side, and must not be used when the audio was not
emphasized.
The analog audio goes through an output level control and then goes to the output
amplifier. The RX LEVELS and red OVERLOAD indicators, which are
calibrated the same as those on the PT-150C, monitor the digital signal sent to the
digital-audio converter (DAC).
The amplifier produces a balanced two-channel audio output with a maximum
signal level up to +24 dBm, referenced to 600 ohms. Equipment jacks are
provided for test signal retrieval, and switches behind these jacks enable them to
be used for output monitoring as well. Output level controls on the front edge of
the module are factory preset to the calibrated level, and the output impedance is
less than 105 ohms.
A green SRVC indicator stays on when the PR-150C is powered and operating.
Red FAIL indicators on the front of the PR-150C show failure of the
corresponding channel's DSP.
