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1781 Mic/ Line Input Module
DESCRIPTION
The ELECTRO-VOICE 1781A program mable input module
accepts either mic or line level signals through a wide variety of
connector interfaces. Standard features include an electronically
balanced input stage with adjustable gain, continuously variable
high and low pass filters, RFI protection, 36 volt phantom
powering two levels of muting, and remote control capability.
Programming is accomplished with plug-in jumpers which may
select phantom power (on or off), mute priority or slave, or remote
volume control. ELECTRO-VOICE also offers the 1781AT, a
programmable input module with a Transformer installed.
INSTALLATION OF OPTIONAL 1785A INPUT ISOLATION
TRANSFORMER
1. Remove the two wire jumpers with ferrite beads,
designated FB1 and FB2, near the upper right corner of
the module when looking at the component side of the
circuit board. Refer to Figure 1 for details.
2. Thread the four wires from the transformer through the
larger center hole from the component side. Secure the
transformer with the two screws and washers provided.
3. Lay the module on the component side (circuit side up)
and attach the four wires as shown in Figure 2.
CONFIGURING THE 1781A
A block diagram of the 1781A input module is shown in Figure
3. Study the diagram carefully and refer to it as needed.
PROGRAMMING THE 1781A
Mute"Priority" Mode of Operation
In the priority mode, a signal applied to the designated priority
channel will cause all other input channels configured in the
slave mode to be fully attenuated.
To configure an input module for the priority mode, install a
2-pin female jumper onto J4, the 2-pin male header connector
located near the lower right corner of the module as shown in
Figure 1.
Any number of channels can be configured in the priority mode,
however, activity in one priority channel will not attenuate the
other priority channels.
Mute "Slave" Mode of Operation
In the slave mode, a module (or all slave modules) will be fully
attenuated either during activity in the priority channel, switch
closure between the MUTE and COM (common) terminals of
the 7-lug screw terminal connector located on the rear of the
mainframe, or a switch closure between the common and any
one of the tone generator control inputs (for the duration of the
tone).
Figure 1. Optional 1781A Configuration
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