Table of Contents
Advertisement
-
-
-
-
-
-
RF
INPUT
OFFSET
MOOULATlON
I
1----___,I,..::.J;::.,S .,.. 10.7 MHZ
I
IF
I
I
- - - - - - - - - - - - - - - : I . . : : . . : J 6 ' - DUPLEX
· -
I
OUTPUT
1 - - - - - - - - - - - - - - + 1
J;.;..7...,.
OFFSET
I
FREO
_________ _j
8521-40
Figure 5-7.
Duplex Generator Block Diagram
5-56.
Code Synthesizer
5-57.
Three simultaneous modulation sources are possible with the internal Code Synthesizer. A private line
(PL) or Digital Private Line (DPL) source, a fixed 1 kHz source, and external modulation sources are
individually level controllable and sumed together to give the composite modulation audio. The Code
Synthesizer provides the modulation source for the system in the generate mode and can be used as an audio
frequency source when in the monitor mode. For the IEEE option a provision is made to allow processor
control of the modulation levels. A block diagram of the Code Synthesizer is shown in figure 5-8.
5-58.
The PL signaling sequence generator is an Audio Synthesizer with an output frequency range from 5Hz
to 10 kHz in 0.1 Hz steps. The frequency is programmed by the processor in response to the operator's request
from the keyboard through the CRT display. The Programmable Attenuator following the synthesizer provides
10 dB and 30 dB attenuation levels for the tone remote access sequence.
5-59.
DPL Code words are generated by the processor in response to the code entered by the operator. The
23-bit DPL word is stored in the DPL Generator and continuously output when selected. Either PL or DPL
signals are switched to the Code Synthesizer Level control on the front panel.
5-60.
A
1
kHz reference signal from the RF Synthesizer is bandpass filtered to provide a low distortion
1 kHz
sinewave to the front panel 1 kHz Level Control.
5-61.
Two sources of external modulation are possible. A standard Motorola microphone interface jack on
the front panel and a BNC front panel jack are provided. The microphone input is connected to an IDC circuit
. for peak limiting. The composite of the two external modulation sources is the signal to the External Level
control on the front paneL
5-62.
Systems without the IEEE option will have the wipers of the level control pots jumpered to their
respective inputs to the summation amp on the Audio Synthesizer module (A6). Those systems with the IEEE
option will select on the IEEE Interface module (AS) either the tops of the level controls or their wipers to the
Programmable Attenuators for remote or local control respectively. While in the IEEE Control mode the
processor controlled Programmable Attenuator on the IEEE module provides the modulation level control. For
the local mode the attenuators are programmed for zero attenuation so that the wipers of the level controls set
the modulation levels directly.
5-15
Advertisement
Chapters
Table of Contents
