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load using no cable. The circuit
shown in Figure A2 only uses the TXP pin and pro-
vides the proper output impedance and drive level
using standard 1% resistors. The connector for con-
sumer would be an RCA phono socket. This circuit
is also short circuit protected.
The TXP pin may be used to drive TTL or CMOS
gates as shown in Figure A3. This circuit may be
30
The transformer should be capable of operating
from 1.5 to 14 MHz, which is the audio data rate of
25 kHz to 108 kHz after biphase-mark encoding.
Transformers provide isolation from ground loops,
60Hz noise, and common mode noise and interfer-
ence. One of the important considerations when
choosing transformers is minimizing shunt capaci-
tance between primary and secondary windings.
The higher the shunt capacitance, the lower the iso-
lation between primary and secondary, and the
more coupling of high frequency energy. This en-
ergy appears in the form of common mode noise on
the receive side ground and has the potential to de-
grade analog performance. Therefore, for best per-
formance, shielded transformers optimized for
minimum shunt capacitance should be used. The
following are a few typical transformers:
Pulse Engineering
Telecom Products Group
7250 Convoy Ct.
San Diego, CA 92111
DS239PP1