Manual

Issue 2, January 2020 Model 47A User Guide
Page 20 Studio Technologies, Inc.
DC power source. (This scenario would be
the same as provided by the Studio Tech-
nologies’ Model 46A Intercom Interface.)
For example, if a single-channel Clear-Com
party-line intercom circuit is directly con-
nected to a Model 47A then the DC power
present on pin 3 would cause the call light
function on any connected Clear-Com user
beltpacks to be enabled. (Unlike BP-325
beltpacks which use 20 kHz tones to en-
able the call function, single-channel Clear-
Com uses a DC voltage on pin 3 as it’s call
light indication.)
An advanced configuration parameter al-
lows the DC power sources for pin 3 of
each interface to be disabled; terminating
impedances for pin 3 continues to be ap-
plied normally. Referring to Figure 9, when
DIP switch 3 is in its off (down) position
normal Model 47A operation will take place.
When DIP switch 3 is in its on (up) position
the ability to enable power sources for pin
3 of each interface will be disabled. Note
that in this mode each interface’s mode DIP
switches, accessible on the front panel, will
still function normally overall. The exception
being that when a mode DIP switch 1 is in
its on (up) position DC power is only pro-
vided to pin 2; terminating impedances will
still be applied to both pins 2 and 3.
It’s not expected that advanced configu-
ration DIP switch 3 on a Model 47A unit
will typically be selected to disable pin 3
power. It’s there as a resource for spe-
cial situations. The ability to disable pin 3
power is really only provided for infrequent
application-specific situations. If an instal-
lation requires that switch 3 be set to its
on (up) position all the time then it would
be worth reviewing if the lower-cost Model
46A be more appropriate.
Factory Test
Back-panel DIP switch 4 is used to select
between normal mode and factory test
mode. Referring to Figure 10, when DIP
switch 4 is in its off (down) position the
Model 47A operates in its standard fash-
ion. When DIP switch 4 is in its on (up)
position the factory test mode is selected.
As expected, when the Model 47A is
deployed in the field DIP switch 4 should
remain in its off (down) position. No dam-
age to the Model 47A or connected equip-
ment will occur when factory test mode is
active.
Figure 10. DIP Switch 4—Factory Test
Figure 9. DIP Switch 3—Pin 3 Power Disable