CANOGA PERKINS 2270 Fiber Optic Modem - Manual (Page 32)

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Canoga Perkins
3.6.2 DS1 / T1 Model -T1
This interface is compatible with AMI-coded T1 data only. If line coding is other than AMI, such as
B8ZS, then a model B type interface must be used.
NOTE: This interface corrects bipolar violations. If these violations must pass through for
fault detection, a model B type interface must be used.
NOTE: This interface is compatible with clock and data transmission. The other end of
the link can have a variety of interfaces (e.g., -32, -22, -35, etc.), if required.
A special four-position feed-through terminal block is provided for connecting the T1 twisted pairs
to the 2270 modem. The standalone version has the terminal positions marked on the rear of the
unit.
The DS1/T1 rack-mount versions do not have any external indication as to which pair should be
connected to which terminals; however, these positions are indicated on the circuit board. When
viewing the 2201 Rack Chassis from the rear, the upper two terminals are for the transmit pair and
the lower two are for the receive pair.
The T1 interface wires are secured by inserting them into the square aperture under the terminal
screw. Tightening the terminal screw clamps the wire in position.
An access hole for a diagnostic probe is provided above the clamping screw.
NOTE: When using the DS1/T1 interface, the modem must be configured for external
clock.
3.7 TTL/BNC Interface Model -BN
This model uses BNC (bayonet) connectors for the physical interface. The electrical signal char-
acteristics are unbalanced TTL levels, with only the clock and data circuits supported. Four BNC
connectors are supplied for connection to a DTE device.
High speeds and long distances (clock and data only) can be achieved using this interface.
This interface version has a switchable dual purpose port for the Send Timing (SCT) and Terminal
Timing (SCTE) clock signals. A two-position slide switch (S1) on the interface card controls the
port direction.
When the switch is set towards the BNC connectors, the port is configured as an input (for the
SCTE clock). Sliding the switch away from the BNC connectors configures the port as an output
(for the SCT clock). (See Figure 3-6 for connectors and refer to Table 3-K for signals supported.)
NOTE: When setting up the clock select, the proper main circuit board clock mode must
be set correctly, i.e., external for the SCTE clock input, slave or internal for the SCT clock
output.