Motorola MSF 5000 Instruction Manual page 82

Chapter
1
Description
MSF
5000
Instruction Manual
Secure
Board Functional Description
The output of this filter is
sent to the
SSCB, where it is summed with
other signals
to be sent
down
the
wireline. If
the station is
configured
as a
transparent
repeater,
the reclocked received data is routed
to the
transmit path
as
well
as to the
wireline.
Receive Audio Decryption
Operation
Audio
for
decryption originates
at the station receiver and enters the Secure board
at the
QUAD AUDIO input. This signal is re-clocked, buffered, and routed
to
secure
hybrids
for decryption. The recovered clock
is
supplied
to the rest of the
circuitry processing
the
signal.
Any
secure
hybrid operating in
the receive mode
attempts
to
decrypt
the
received signal.
In
half-duplex operation, any
one of eight secure
hybrids
can be selected for
decryption. In full-duplex operation, only four
secure
hybrids
can be selected for
decryption. Refer
to
Table
1-8.
Table
1-8
Local Control Key/Hybrid Selection
Front Panel
Half-Duplex
Full Duplex Operation or DVP
Status Display
Operation Operation (half-duplex)
'Key
Digit Encrypt
&
Decrypt
Encrypt
Decrypt
1
HY4001A HY4001A HY4001B
2
HY4002A HY4002A
HY4002B
3
HY4003A
HY4003A HY4003B
4
HY4004A HY4004A HY4004B
HY4001B
HY4002B
HY4003B
HY4004B
5
6
7
8
The RX DATA signal, DECRYPT AUDIO,
is sent
to a
D/A
converter, reproduce
the
original audio signal. The
D/A
conversion is performed for half and full-duplex
operations.
The proper code detect function is also performed. This function
indicates
if
the coded transmission being received used the same
encryption key
as stored in the Secure board
encryption hybrid.
The recovered audio output
is routed through an active bandpass filter to
improve audio quality and remove out-of-band
noise.
This signal may
be
amplified
or attenuated
+/-
10
dB
by adjusting
the
gain stage
with
EEPOT
No.
0
on the front panel Status display.
Normally,
the
level of
the
decrypted audio
should
be set 4
dB
higher
than clear audio.
Finally,
the signal is gated and sent
to
the
SSCB where it is summed with
other signals to
be
sent
down
the
wireline.
1-44
68P81092E02
3/14/94
Chapter
1
Description
MSF
5000
Instruction Manual
Secure
Board Functional Description
The output of this filter is
sent to the
SSCB, where it is summed with
other signals
to be sent
down
the
wireline. If
the station is
configured
as a
transparent
repeater,
the reclocked received data is routed
to the
transmit path
as
well
as to the
wireline.
Receive Audio Decryption
Operation
Audio
for
decryption originates
at the station receiver and enters the Secure board
at the
QUAD AUDIO input. This signal is re-clocked, buffered, and routed
to
secure
hybrids
for decryption. The recovered clock
is
supplied
to the rest of the
circuitry processing
the
signal.
Any
secure
hybrid operating in
the receive mode
attempts
to
decrypt
the
received signal.
In
half-duplex operation, any
one of eight secure
hybrids
can be selected for
decryption. In full-duplex operation, only four
secure
hybrids
can be selected for
decryption. Refer
to
Table
1-8.
Table
1-8
Local Control Key/Hybrid Selection
Front Panel
Half-Duplex
Full Duplex Operation or DVP
Status Display
Operation Operation (half-duplex)
'Key
Digit Encrypt
&
Decrypt
Encrypt
Decrypt
1
HY4001A HY4001A HY4001B
2
HY4002A HY4002A
HY4002B
3
HY4003A
HY4003A HY4003B
4
HY4004A HY4004A HY4004B
HY4001B
HY4002B
HY4003B
HY4004B
5
6
7
8
The RX DATA signal, DECRYPT AUDIO,
is sent
to a
D/A
converter, reproduce
the
original audio signal. The
D/A
conversion is performed for half and full-duplex
operations.
The proper code detect function is also performed. This function
indicates
if
the coded transmission being received used the same
encryption key
as stored in the Secure board
encryption hybrid.
The recovered audio output
is routed through an active bandpass filter to
improve audio quality and remove out-of-band
noise.
This signal may
be
amplified
or attenuated
+/-
10
dB
by adjusting
the
gain stage
with
EEPOT
No.
0
on the front panel Status display.
Normally,
the
level of
the
decrypted audio
should
be set 4
dB
higher
than clear audio.
Finally,
the signal is gated and sent
to
the
SSCB where it is summed with
other signals to
be
sent
down
the
wireline.
1-44
68P81092E02
3/14/94