Issue 1, September 2014
Model 46A User Guide
Page 20
Studio Technologies, Inc.
Operation
Technician intervention is typically not
required during normal Model 46A opera-
tion. The unit is designed for continuous
operation with no routine maintenance
necessary. Activating the auto null func-
tions may be warranted should connected
user devices or wiring associated with the
2-wire party-line intercom be changed.
Upon power-up the Model 46A will go
through a short initialization sequence
before normal operation will begin. The
power and status LEDs will each light
sequentially and, upon completion, the
power LED will light steadily. The settings
for the four hybrid circuits are stored in
non-volatile memory and will be recalled
during the power-up process.
Level Meters
The Model 46A contains eight 5-seg-
ment LED level meters. These meters
are provided as a support aid during
installation, configuration, operation, and
troubleshooting. The meters represent the
signals coming in from, and going out to,
the 4-wire connections. The meters are
organized in four groups each represent-
ing one input and one output. They are
calibrated to reflect the level in dB relative
to the configured nominal operating level.
This is similar to the way in which now-leg-
acy VU meters functioned. As an example
let’s take the situation where the nominal
operating level of interface 1 is configured
for +4 dBu. The LEDs labeled –18, –12,
–6, and 0 of the TO 4-wire ch 1 meters are
lit. (For this example, the level on pin 2 of
interface 1’s 2-wire PL circuit is just large
enough to light the 0 LED.) This indicates
that a signal with the approximate level
of +4 dBu is present on the associated
4-wire output connector. Another example
would be a Model 46A interface configured
for +8 dBu operation and –18 and –12 dB
LEDs are lit. This would indicate that a sig-
nal with an audio level of approximately
–4 dBu is present on its associated output.
Each level meter contains four green LEDs
and one yellow LED. The four green LEDs
indicate signal levels at or below the con-
figured nominal level. The top LED is yel-
low in color and indicates a signal that is
6 dB or greater than the nominal level. An
audio signal that causes the yellow LED to
light doesn’t necessarily indicate an exces-
sive level condition, but it does provide a
warning that at some stage reducing the
signal level may be prudent. Operation with
normal signal levels should find the meters
lighting near their 0 dB point. Signal peaks
may cause the yellow LEDs to flash. But a
yellow LED that lights fully during normal
operation will typically indicate a signal
level or configuration problem.
If the FROM 4-wire meters display consis-
tency lower or higher levels than their 0 dB
points it’s possible that a configuration is-
sue exists. One potential problem is incor-
rectly set 4-wire nominal audio level DIP
switches for one or both of the Model 46A’s
interfaces. If the nominal level is set too
low then sufficient audio headroom might
not be available. It can also result in ex-
cessively-high audio signals being sent to
2-wire party-line circuits. Setting the nomi-
nal level for too high a value will reduce the
signal-to-noise performance. And, as ex-
pected, it may also result in audio signals
being sent to the 2-wire circuits at too low
a level. Begin a review by confirming that
the two 4-wire level DIP switches associat-
ed with each interface are set as required.
