Shure SCM410E manual Inhibiting Gating for Unwanted Sounds, Loudspeaker Muting, Filibuster Mode

INHIBITING GATING FOR UNWANTED SOUNDS

MaxBus attempts to activate only one microphone per sound source. Muting a microphone channel prevents its audio from appearing at the

An existing sound system using 24-volt relays can be used with the SCM410 without modification if the relay coil current draw is under 500 mA.

mixer's output. However, the muted microphone still communicates with other mic channels via MaxBus. A sound source picked up by a muted mi- crophone will not activate other microphones.

Sound sources that may cause unwanted microphone channel activa- tion include:

•Heating, ventilation, or air conditioning systems

•A noisy fax machine or printer

•A squeaky door

•A paging system loudspeaker

•An audio teleconferencing return signal loudspeaker

The SCM410 can prevent these and similar sounds from activating microphones as follows:

1.	Place one microphone near the unwanted sound source. Con-
	nect that microphone's signal to a channel input, -or- connect the
	unwanted sound source directly into a channel input.
2.	Mute that channel using the logic terminal (see Figure 11). To
	perform this modification internally on the mixer, refer to the
	Shorting Mute In to Logic Ground Internally paragraph in the
	Internal Modifications section.
3.	Adjust the channel gain control just past the level where
	unwanted sounds do not activate other microphones in the

D D

G1

D = 1N4148

+

12 V POWER

SUPPLY

–

LOGIC

GROUND

G3

system. If the channel gain is set too high, the other micro-

phones may not be activated by the desired sounds. If set too

low, unwanted sounds will continue to activate other micro-

phones.

LOGIC

GROUND

M1

INHIBITING GATING FOR UNWANTED SOUNDS

FIGURE 11

LOUDSPEAKER MUTING

Some applications require a loudspeaker to be placed near each talker to provide audio reinforcement, or to permit telephone conversation or conference monitoring. Each loudspeaker 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 sep- arate loudspeaker muting relay (See Figure 12). Recommended relays are Radio Shack 275-248, Omron G2R-14-DC12 (Digi-Key number Z745-ND), Potter & Brumfield R10-E1Y2-V185 (Newark number 45F106), or equivalent.

NOTE: A diode across each relay coil is required to suppress inductive voltage spikes which may damage the SCM410.

LOUDSPEAKER MUTING

FIGURE 12

“FILIBUSTER” MODE

Normally, when several people talk, each microphone gates on so that no speech is missed. In “filibuster” mode, a microphone remains gated on until the talker pauses long enough for that microphone to gate off. No other microphone can gate on until that microphone gates off. This pre- vents talkers from being interrupted.

To establish filibuster mode, refer to Figure 13 and proceed as follows:

1.Perform the Mute to Inhibit modification as presented in the Internal Modifications section.

2.Connect all the MUTE IN pins together on the modified channels.

3.Connect all the GATE OUT pins together on the modified channels.

4.Connect the GATE OUT pin of one modified channel to the MUTE IN pin of another modified channel .

5.Turn the Last Mic Lock-On switch to OFF.

NOTE: To prevent high-frequency oscillation, do not wire a GATE OUT pin to a MUTE IN pin on the same channel unless the Mute to Inhibit modification has been made.

	LOGIC
G1 G2 G3	GROUND

M1 M2 M3

“FILIBUSTER” MODE

FIGURE 13

12