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.