JK Audio PBXport - Manual (Page 8)

8
Operation (continued)
A-B-C Selector Switch
Use this switch to select the correct type of handset micro-
phone that your telephone uses. A=Electret, B=Carbon,
C=Dynamic. Trial and error seems to work best in determin-
ing which handset type to use. Your PBXport will only func-
tion correctly if the handset type selector switch is in the cor-
rect position. This switch changes signal level, impedance,
and wiring to accommodate the differences in handset micro-
phone types.
In order to determine the correct position, you must place a
call to a nearby telephone, then try to send audio into the
PBXport through the inputs. While doing this, switch between
the three different handset type positions. Choose the posi-
tion that works best by monitoring the audio quality and send
LED's. You may need to readjust the Send audio level for
each setting.
Although not conclusive, the following guidelines may help:
The majority of newer telephones have electret type micro-
phones and will use the "A" position.
Older telephones that have the round "screw-on type" hand-
sets contain carbon microphones and use the "B" position.
Many Radio Shack
® , Panasonic ® , and Nortel ® telephones
have dynamic microphone types and use the "C" position.
9
Operation (continued)
Optional Jumper Settings
If your unit was purchased after December 2007, there are
two jumpers located on the circuit board inside the PBXport
that affect your incoming audio. The jumper at J10 allows you
to completely disable both the handset microphone and
speaker when the Online button is pressed. The factory de-
fault closed position disables only the handset microphone
when the Online button is pressed. This will have no affect on
normal telephone operation.
If the incoming audio level from your telephone is too high
and you are consistently lighting the red –3 dB Receive LED,
first try decreasing the volume using the controls on the base
of your telephone. If you still cannot drop the incoming audio
level enough, you may need to change jumper J11. There
are three possible settings to adjust Caller Receive level:
Pins 1 & 2 closed = 0 dB (factory default)
Pins 2 & 3 closed = -10 dB
Pins 1-3 left open = -20 dB
To change the jumper settings, first disconnect power from
the PBXport, then remove the top cover on the unit. Locate
the appropriate jumper on the printed circuit board and set to
the desired position.
WARNING! The AC cable must be unplugged from
the back of PBXport anytime the case is opened. Fail-
ure to follow these instructions could potentially result
in injury or death.
ATTENTION! Be sure to use an ESD grounding
wrist strap when changing this jumper setting. If you
do not have a wrist strap, keep one hand on the
PBXport case at all times while changing the jumper
with the other hand. These measures are required to
prevent electrostatic discharge from damaging the
unit.
Operation (continued)