AB-120 Announcer Console
Internal jumpers JP9 and JP10 are normally factory set for -60 dB (dynamic microphone).
Line Output Level Select
The operating level at the output is selectable to accommodate the various types of devices
that are to be fed. The microphone input of a console would need -60 dBu whereas the line
input of a console might need a level of -10 dBu.
Jumper JP8 allows the selection of gain for the output amplifier and the output connector on
the rear panel can be plugged into an alternate header on the printed circuit board that has a
30 dB pad inserted in the output. The combination of JP8 and the 30 dB pad allows an output
level selection from 0 dBu to -50 dBu in 10 dB steps.
0dBu
-10dBu
-20dBu
-30dBu
-40dBu
-50dBu
Output Connector
J2
J2
J2
J3
J3
J3
JP8 Position
Open
2-3
1-2
Open
2-3
1-2
The output gain is normally factory set to -10 dBu.
Options for Power
The AB-120 can be powered from the intercom line, the IFB line, or from a local external DC
supply. To power it from the intercom line of the IFB line, the unit needs a minimum of 25
VDC. The AB-120 draws approximately 100 mA of current with peaks of 120 mA.
Power from the IFB Line
To power the unit from the IFB line, set jump jacks on pins 2 and 3 of JP5. JP5 selects where
the positive DC power is sourced from.
If for noise reasons, pin 1 of the IFB input connector can not be connected to power ground of
the AB-120, the power cannot be derived from the IFB line.
Power from the Intercom Line
To power the unit from the intercom line, set jump jacks on pins 1 and 2 of JP5. JP5 selects
where the positive DC power is sourced from.
Power from an External DC Supply
If power from the intercom line or IFB line is not available then plug in the DC supply supplied
with the unit.
2.3.2
Rear Panel Connectors and Controls
The rear panel of the AB-120 has the following connectors and controls.
Page 10
