Shure SCM810 User Manual page 12

3. Adjust that channel's gain control just to the level where oth-
er microphones in the system do not activate for the un-
wanted sound. If the channel gain is set too high, other sys-
tem microphones will be difficult to activate for desired
sounds. If set too low, unwanted sounds will continue to acti-
vate other microphones.
M1
INHIBITING GATING FOR UNWANTED SOUNDS
FIGURE 15
Loudspeaker Muting
Some applications require a loudspeaker to be placed near
each talker to provide audio reinforcement, or to permit tele-
phone conversation or conference monitoring. Each loud-
speaker can cause feedback unless it is automatically
switched off when the talker near it speaks. To provide this
function, connect the GATE OUT terminal of each channel to a
separate loudspeaker muting relay as shown in Figure 16
(Channels 1, 3 and 5 shown modified). Recommended relays
are Omron G6B-1174P-US-DC12, Potter & Brumfield
R10-E1Y2-V185, or equivalent (available through Digi-Key
and Newark Electronics). NOTE: A diode across each relay
coil is required to suppress inductive voltage spikes which may
damage the SCM810.
An existing sound system using 24-volt relays can be used
with the SCM810 without modification if the relay coil current
draw is under 500 mA.
"Filibuster" Mode
In normal operation, when several people talk, each micro-
phone gates on so that no speech is missed. In "filibuster" ac-
tion, a microphone that is gated on prevents other micro-
phones from gating on. Once a microphone has gated on, oth-
er microphones cannot gate on until the talker has paused long
enough for that microphone to gate off. Thus the person talking
has the floor and cannot be interrupted.
To establish this function, first perform the internal Mute to
"inhibit" modification (see Internal Modifications ). Then con-
nect all the MUTE IN pins of the modified channels together, all
the GATE OUT pins of the modified channels together, and the
GATE OUT pin of one modified channel to the MUTE IN pin of
LOGIC
GROUND another modified channel (see Figure 17 -– Channels 1, 2 and
3 modified). Turn the Last Mic Lock-On switch (SW702, posi-
tion 2) to off.
NOTE: To prevent high-frequency oscillation, do not wire a
channel's GATE OUT pin to its own MUTE IN pin unless the
Mute to "Inhibit" change has been made.
Inhibit Function
See Internal Modifications .
Diode Isolation of Logic Controls
Two or more control functions using the same logic pins can
be isolated with diodes. In this manner a channel can be muted
by an overall group mute switch, or by its own cough button
(see Figure 18 -– Channels 1, 3 and 5 modified).
GROUP
MUTE
COUGH
BUTTONS
External Logic Devices
SCM810 logic levels are directly compatible with TTL and
5-volt CMOS logic families. For information on logic gate use,
refer to the TTL Cookbook and CMOS Cookbook , both by D.
Lancaster, Howard Sams Publishing Co.
Mixer logic may be used with 15-volt CMOS logic if a pull-up
resistor is used with each GATE output (see Figure 19 -–
Channel 1 modified).
12
D = 1N4148 OR
EQUIVALENT
M1 M3 M5
DIODE ISOLATION OF LOGIC CONTROLS
FIGURE 18
LOGIC
GROUND