Studio Technologies IFB Plus 2001 - Manual (Page 21)

Model 2 User Guide Issue 7, November 2001
Studio Technologies, Inc. Page 21
to either IFB channel 1 or 2, but not to
both simultaneously.
The VOX interrupt function is only sophisti-
cated from an internal-circuitry stand
point. Operation is quite simple, with
only two switches to set. The input switch
allows one of three audio sources to be
connected to the VOX input: audio from
the auxiliary audio input, receive audio
from telephone interface 1, or receive
audio from telephone interface 2. The
output switch is used to select whether the
VOX interrupt function is off (not used), or
is assigned to interrupt IFB channel 1 or 2.
VOX operation can commence as soon as
the output is assigned to one of the chan-
nels. VOX interrupt activity can be noted
by observing the yellow VOX LED associ-
ated with the assigned IFB channel.
Telephone Interface 1
Two status LEDs, one switch, and one trim
potentiometer are associated with tele-
phone interface 1. The yellow LED, la-
beled STD, is lit whenever the interface
is set for the standard audio mode by the
switch on the back panel. The red LED,
labeled LC for loop current, lights any time
DC current is flowing through the inter-
face. Normally in the standard audio
mode, loop current would not be flowing
through the interface and the LC LED will
not be lit. In most cases the loop current
LED lighting would indicate that the mode
switch should be changed to the tele-
phone line position.
The interface control switch, active in the
telephone line mode, allows the interface
to be taken off hook or hung up. Momen-
tarily pressing the switch to the up posi-
tion, labeled MAN OH for manual off hook,
places the interface in the off-hook state.
If loop current is detected, the interface
will stay in the off-hook state and the loop
current LED will light. If loop current is not
detected, the interface will return to the
off-hook (idle) state after a few seconds.
Momentarily pressing the switch to the
down position, labeled HANG UP, immedi-
ately disconnects the interface from the
telephone line. In the standard audio
mode, the interface control switch is not
active because the standard audio mode
places the interface permanently in what
is effectively the off-hook condition.
Telephone line audio signals can vary
greatly in level on a call-by-call basis. To
counter this problem, a level trim potent-
iometer is provided for the operator, allow-
ing adjustment over a ±8dB range. A
quiet signal can be boosted, and a “hot”
signal can be attenuated. The trim pot is
accessible via a small hole in the front
panel, directly to the right of the interface
control switch.
Telephone Interface 2
Two status LEDs, two switches, and one
trim potentiometer are associated with
telephone interface 2. The yellow LED,
labeled STD, is lit whenever the interface
is set for the standard audio mode by the
switch on the back panel. The red LED,
labeled LC for loop current, lights any
time DC current is flowing through the
interface. In the standard audio mode,
loop current will not usually be flowing
through the interface. If it is, the red LED
will light. In most cases the loop current
LED lighting would indicate that the mode
switch should be changed to the tele-
phone line position.
The interface control switch, active in
the telephone line mode, allows the inter-
face to be taken off hook or hung up.
Momentarily pressing the switch to the