C.E.S. Model SDI-50 Manual, Level Adjustments
a sufficient level can't be obtained, cut JMP2 to increase the gain of
the receive amp U13 and re-try. This completes the RX VOICE LEVEL
adjustment.
5.3
TRANSMIT VOICE LEVEL R75
(6,C) This adjustment is used to set the signal level from the
telephone line to the radio transmitter. To adjust the TRANSMIT VOICE
LEVEL, adjust your service monitor to listen to the output frequency
of the transmitter. Adjust the Transmit Voice Level, R75, to 4.0 Khz
deviation. If you encounter difficulty setting this level because the
potentiometer is overly sensitive then remove JMP5.
5.4
HYBRID BALANCE R40
(5,B) The Hybrid Balance adjustment is used in "full duplex" systems
only (where mobile stations are capable of receiving and transmitting
simultaneously). If your system is "half duplex" or simplex, (where a
mobile can only transmit, or receive at a given time), then this
adjustment may not be required. This adjustment cannot be made unless
the interconnect is programmed for "full duplex" operation.
The hybrid balance adjustment should be performed on the phone line
which the interconnect is to be used on. Durring adjustment, the SDI-
50 will have to be in the Connect Mode on a quiet line. To achieve
this, call into the interconnect and answer the call by pushing the
Connect button. Or, call time and temperature, and wait for the
recording to stop.
Set your service monitor to generate an 800 Hz. audio signal at 4.0
kHz deviation on the receive frequency of your system, allowing the
signal to pass through the hybrid circuit and back out through the
TRANSMIT AUDIO OUTPUT. The calling party will also hear this tone.
Now while watching the deviation level of the signal generated by the
Model SDI-50, adjust the HYBRID BALANCE adjustment, R40, for a minimum
signal in the deviation level. This adjustment is critical, and if a
sharp null is not found by turning the HYBRID BALANCE through a
complete rotation, then an additional compensation capacitor may be
required to match the telephone line impedance. Install a value from
.047uf to .47uf in the location for C28, near the HYBRID BALANCE
adjustment. After this capacitor is installed, try again to adjust
the HYBRID BALANCE for a null. If the null is still not satisfactory
then repeat this capacitor substitution process until until an
acceptable null is achieved.
5.5
TONE OUTPUT LEVEL R68
(6,C) Set your service monitor to receive on your transmit frequency.
Dial the phone number of the telephone line connected to the SDI-50.
After the SDI-50 answers and returns
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