OVERVIEW

corresponding IC pin.
evaluation of the XR-T3588 line driver and the XR-T3589
line receiver devices in a CCITT V.35 application. Its
features include dip switch selection of channel
power-down options, and provisions for applying the
ground potential offset voltage specified by the V.35 test
procedure to the receiver inputs. Figure 1., Figure 2. and
Table 3. show the demo board component layout, circuit
diagram and list of components respectively. 

POWER REQUIREMENTS

Supply voltages of +5.0V 5% for VCC and -5.0V 5%
for VEE are applied to the board through banana jacks.
Both power sources should be well-regulated, and each
must be capable of supplying 250mA minimum. During
normal operation jumper E-1 must be installed, and
nothing is connected to the banana jack labeled OFFSET. 

XR-T3588 DIGITAL INPUT AND XR-T3589 DIGITAL OUTPUT CONNECTIONS

The TTL compatible transmitter inputs are the BNC
connectors mounted on the left side of the board that are
labeled TX1IN, TX2IN and TX3IN. Provisions are
included for installing input termination resistors R1, R2,
and R3 if required. These resistors (50 or 75W) are
needed only if a pulse generator with a low impedance
output and a fast rise time is used as a test signal source.
They are not required for TTL signals applied to the board
through short cables.
Likewise, the TTL compatible receiver outputs are the
BNC connectors labeled RX1OUT, RX2OUT and
RX3OUT.

XR-T3588 LINE OUTPUT AND XR-T3589 LINE INPUT CONNECTIONS 

The line connections are made to the six RJ-11
connectors or to the corresponding test point pairs that
are located on the right side of the board. The RJ-11s are
for connecting twisted pair cables, and the test points
provide a convenient means for viewing the output and
input signals differentially on an oscilloscope. From top to
bottom, the three transmitter outputs are labeled
TX1OUT, TX2OUT, and TX3OUT, and the three receiver
inputs are labeled RX1IN, RX2IN, and RX3IN. Note that
connectors are wired so that the “A” and “B” XR-T3588
output pins and the “A” and “B” XR-T3589 input pins go to
the same pin numbers on the RJ-11 connectors.
Therefore, a test cable must be wired in the same manner
to prevent a data inversion between the transmitter digital
input and the receiver digital output. (Telephone cables
typically contain a “twist” between modular connectors,
and will therefore give a data inversion.)

TRANSMITTER AND RECEIVER POWER-DOWN

The four-position DIP switch located in the center of the
board selects the logic state applied to the transmitter and
receiver channel enable pins. The top two sections
labeled TX, and the bottom two sections labeled RX are
for the XR-T3588 and XR-T3589 respectively. Table 1.
and Table 2. show the powering options. Note that when
a DIP switch section is “OFF,” a logic 1 is applied to the
corresponding IC pin.​