Nortel T1/SMDI Configuration Manual page 175

February 2008
If a modem or other equipment is necessary to connect CallPilot to the
switch (for example, RS-232 physical link of the SMDI protocol link
distance exceeds 15 meters), perform the following: select a modem or other
equipment that meets the particular application requirements, contingent on
the physical link interface characteristics at the CallPilot RS-232
demarcation point conforming to this document. For example, you can use
the same modem at each end of the analog line, thus ensuring compatibility.
One stipulation of the RS-232 standard is that the maximum RS-232 cable
length is constrained such that the cable interchange capacitance of the
entire link does not exceed 2500 pF. In applications where the cable
interchange capacitance exceeds 2500 pF, use a network engineered
solution that respects the RS-232 standard, yet allows the range of the entire
SMDI connection to be extended. This is typically achieved by the use of
either short-haul or long-haul modems and a network communication link
(depending on application requirements) as shown in the following
conceptual diagram:
SDMI link extension beyond the RS-232 demarcation line
Transmitted data
DTE
Computer
T1/SMDI and CallPilot Server Configuration
Simple serial data communications link
RS-232
DCE
Modem
Communications
link
CallPilot T1/SMDI interfaces
Received data
RS-232
DCE
Modem
DTE
Computer
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