Lesson 2/Learning Event 4
(3) Standard plug-in terminating resistors resembling patching plugs
may be used as receive terminating devices at the LINE or EQUIP jacks.
These resistors match the characteristic impedance of the receiving line at
the patch panels, thus minimizing noise buildup in untested segments of the
circuit and on the channels or lines under test.
Learning Event 4: PRECAUTIONS IN TESTING DC CIRCUITS.
Many of the precautions in regard to VF circuits apply also to DC
circuits. The major difference is in the characteristics of signal/current.
Where the important factors in VF transmission are level and frequency the
important factors in DC transmission are the amount of current and its
direction. DC circuits are normally tested at the DC patch bays which are
remote from the VF bays, thus minimizing the possibility of crosspatching
between VF and DC circuits.
DC patching is normally performed in loop
circuits of teletypewriter sets and telegraph terminal equipment. The lint
side of a telegraph terminal is usually VF, so the rules for VF patching and
testing apply here.
Learning Event 5: DESCRIPTION OF DCS TECHNICAL SCHEDULE AND SERVICE.
Selected samples of DCS technical schedules and codes are contained in
the appendix, tables 1 through 5. These technical schedules are established
by DCA, and published in DCAC 300-175-9. They are continually updated and
modified as needed. The specification originates with a request for service
by a user or potential user to satisfy the demands of the requested service.
a. The DCS technical schedule in table 1 is for government owned
circuits.
There are other technical schedules in DCAC 300-175-9 for
communication circuits leased in CONUS, leased from AT&T, and leased from
Western Union, but for this lesson we will stay with the government-owned
circuits.
Within table 1 is listed the circuit categories, circuit types
and type of service for each circuit by item number.
(1) Circuit categories. Listed in table 1 are 10 circuit categories
which have one or more circuit types listed under each category. They are:
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