HP Survivable Branch Communication zl Module powered by Microsoft Lync Planning and Design Guide 2011-02

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Design Considerations
Planning Call Capacity
T1 lines provide 24 voice channels while E1 lines provide 30. Analog Foreign
Exchange Office (FXO) lines support only one call each. Foreign Exchange
Subscriber (FXS) lines connect to analog devices such as fax machines; they
are used to receive calls on behalf of those devices. Table 2-3 displays the
telephony cards supported by the SBM and the number of PSTN calls sup-
ported by each.
However, even if your cards provide more channels, the SBM supports a
maximum of 120 PSTN calls, which is the maximum number of voice channels
provided by a single Four-Port T1/E1 Telephony Card. In other words, install-
ing two Four-Port T1/E1 Telephony Cards in the SBM is not a supported
configuration. If you purchase one of these cards and you use E1, you could
leave the second slot empty or fill it with an FXS option. If you use T1, you
could install a Single-Port T1/E1 Telephony Card or an FXO or FXS option in
the second slot.
Table 2-3. Supported Calls
Estimate Concurrent Calls from Existing Records
You determine the number of channels that you need based on your expected
maximum concurrent calls. The most accurate way to obtain this number is
to check your current usage. If branch users currently use a different PSTN
gateway, check its records. Or, if your branch is currently using a PBX, obtain
those records if possible.
Telephony Card Supported Calls Per-
Interface
Total Supported
Calls Per-Card
Total Supported
Analog Devices
(such as Fax)
Single-Port T1/E1
Telephony Card
T1 = 24
E1 = 30
T1 = 24
E1 = 30
0
Two-Port T1/E1
Telephony Card
T1 = 24
E1 = 30
T1 = 48
E1 = 60
0
Four-Port T1/E1
Telephony Card
T1 = 24
E1 = 30
T1 = 96
E1 = 120
0
Four-Port FXS
Telephony Card
None from Lync users 4
Four-Port FXO
Telephony Card
140
Two-Port FXS, Two-
Port FXO Telephony
Card
FXO = 1
FXS = none (connect
to analog devices)
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