TM 11-7025-221-20
1 - 1 5 . Demultiplexer Section Block Diagram Discussion (V1/V2 Models) - Continued.
Each demux card contains a group strobe generator which is turned on by a FS signal. This syn-
chronizes the group strobe generator with the incoming SG. The group strobe generator produces
a demux strobe for each of the various component parts of the incoming SG. By routing a SG
and a specific demux strobe to another circuit, that circuit will use the strobe to extract (demultiplex)
designated data out of the incoming serial SG data stream. SG and strobe routing to output buffer
cards are controlled by the demux cards in response to configuration data in NVM. Thus, for example,
a SG and a demux strobe for specific group data in that SG are routed from a demux card to
a particular output buffer input. This enables that output buffer to extract designated group data
out of a specific SG.
Output buffer cards A12 through Al 5 provide elastic storage for demultiplexed group data. Each
card contains two output buffers. Buffer length is varied dependent on group data rate under micro-
processor control. For group data rates of 1024 kb/s and 1152 kb/s, an odd numbered buffer is
strapped to its associated even numbered buffer to make one large buffer.
Data are strobed into a buffer by the applied demux strobe. Since the demux strobe is synchronized
to the incoming SG, it contains variations due to satellite path delays. Also, data bits for a given
group are not regularly spaced in the SG. Thus, data are strobed into a buffer at an irregular
rate. Data are clocked out of a buffer by a synchronous buffer output clock timing signal from
PLL card A22.
The output of each buffer is routed through a driver and available in a balanced NRZ format.
Outputs are also available in a TTL format for use by other cards.
Outputs from buffers 1 through 4 are routed to 660 l/O card A3. Drivers on this card convert
the data to an unbalanced NRZ format. If the TD-754 demux option has been selecied, a 1152
kb/s output from buffer 1 and/or buffer 3 will be outputted in parallel, in unbalanced NRZ format,
at ports 1 and 2 or 3 and 4.
660 I/O card A3 also contains circuits to accomplish a multiplexing function normally performed
by a TD-754/G (TD-754 mux option), If this option is selected, the data outputs of buffers 5 and
6 (each at 576 kbs/) are combined by card A3 into a 1152 kb/s signal, routed through the driver
associated with buffer 5, and made available at port 5 in a balanced NRZ format. Similarly, the
outputs of buffers 7 and 8 can be combined and made available at port 7 in a balanced NRZ
format.
Group data outputs from buffers 1, 3, and 5 are applied to group modem card A20. Also, a 16
kb/s orderwire input is received from 16 DVOW card A7. Based on configuration data in NVM,
one of the group data inputs is selected. The orderwire input is also selected if the group data
rate is 256 kb/s or higher. The selected group data input is converted to a conditioned diphase
format and combined with the orderwire, if present, for transmission to the CNCE.
16 DVOW card A7 receives a SG and associated demux strobe from each active demux card.
These inputs are handled on a first-come, first-sewed basis. A ring detector will detect when an
incoming call is for your station. Orderwire data is extracted out of the SG and buffered. Orderwire
data are routed to group modem card A20 and the Vinson driver on SSV card A2 if the call
is secure. Orderwire data for non-secure calls are routed to the H-250 handset.
The Vinson driver on SSV card A2 converts orderwire data received from 16 DVOW card A7 to
a MlL-STD-188-100 format as required by the Vinson.
The loop modem driver on loop modem/rt mess card A4 receives a SG and associated demux
strobe from each active demux card, Based on configuration data in NVM, one SG input will be
selected for processing. Dedicated user data is extracted from the selected SG, buffered, and con-
verted to a conditioned diphase format for output to the dedicated user.
1-19
