MSAN-101 Zarlink Semiconductor, Inc., MSAN-101 Datasheet - Page 6

• Manufacturer Part Number: MSAN-101
• Description: Applications of the MT8804A 8 x 4 Analog Switch Array
• Manufacturer: Zarlink Semiconductor, Inc.

MSAN-101
Switching Network Modularity and
Expansion
The 8 port line interface switching module shown in
Figure 4 would typically be used as the basis for
larger systems such as a PBX. Expansion to a larger
switching network involves two independent steps.
The first involves increasing the maximum number of
simultaneous conversations that can be conducted.
This is referred to as traffic handling capacity, and is
increased by adding MT8804A’s in pairs to the basic
module as shown in Figure 5. The lines (L
extended and connected to those of the new devices.
The junctors (J
are connected together to provide 4 additional signal
paths. The network as shown has 12 signal paths
and hence can carry 6 simultaneous telephone
conversations.
The second expansion step is to increase the
number of 8 port modules. Figure 6 shows the
interconnection between two basic modules of
Figure 4. The signal paths (S
show how the two modules are connected. The
control lines of each module (not shown) would be
connected to the system data bus and appropriate
enabling signals would have to be generated. That
is, each module would also have a unique address.
Combining both expansion steps is exemplified by a
network comprised of two expanded switching
modules of Figure 5. This would result in a system
with 16 ports (telephone lines) capable of handling 6
simultaneous conversations.
A-22
TO SLIC
TRANSMIT
OUTPUTS
TO SLIC
RECEIVE
INPUTS
0
- J
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
3
) of the two additional MT8804’s
J
J
MT8804A
MT8804A
0
0
J
J
1
1
0
J
J
2
2
- S
J 3
J 3
7
) are extended to
Figure 5 - Expanded Switching Module
L
L
L
L
L
L
L
L
0
L
L
L
L
L
L
L
L
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
- L
7
MT8804A
J
MT8804A
J
) are
0
0
J
J
1
1
J
J
2
2
The normal sequence in designing a switching
network involves first establishing the maximum
traffic handling capacity of the system. With this in
hand, the 8 port modules can be designed with the
appropriate number of MT8804A’s. Modular system
expansion would then only involve adding the
required number of such modules. The number of
MT8804A’s required per module and total is shown
in Table 1 as functions of the number of ports to the
network and traffic handling capacity. From the table
it can be seen that there is a one to one relationship
between this traffic handling capacity and the
number of MT8804A’s required in the corresponding
module. This can be used as a design aid in
determining the amount of circuitry required to
implement various sized systems. This information is
expanded in the table of Table 2. Here, is shown the
variation in the number of MT8804A’s required as a
function of traffic handling capacity only in a fixed
256 port system.
J 3
J 3
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
J
J
MT8804A
MT8804A
0
0
J
J
1
1
J
J
2
2
J 3
J 3
S
S
0
11
12 Signal
Paths