Using the Paging Mic, Using the Ambient Mic

Using the Paging Mic

The paging mic is used to make announcements over the system. If the paging mic is a condenser mic or other type of mic that requires phantom power, move the PHANTOM switches to the down position. Otherwise, leave them switched up.

The paging mic can be voice-activated and is routed to all channels or zones. However, you have the option of activating it manually with an external switch. If you choose to use a switch for the paging mic, you have the additional option of assigning the paging mic to either Zone A or to all zones (if multiple SP1200s are used).

•For Zone A only, connect a (normally-open) switch between the ZONE A and GROUND pins on the PAGING MIC CONTROL connector.

•For all zones in a system interconnected via the EXPANSION bus, connect a switch between the ALL CALL and GROUND pins on the PAGING MIC CONTROL connector.

•For maximum flexibility, connect two switches to the PAGING MIC CONTROL connector and have both selections available.

The paging mic can be configured to automatically turn down (duck, or attenuate) the music that is playing over the system so the announcement can be heard when using the VOX circuit. When an announcement is over, the music gradually returns to its original volume.

The music ducks fairly rapidly, attenuating the music 20 dB within 300 ms (milliseconds) of detecting a signal on the paging mic. When the signal on the paging mic stops, there is a 1500 ms (1.5 second) timeout period to make sure the announcement is over, and then the music ramps up to its original volume over the next 2.5 seconds.

Note 1: When manually activating the paging mic, there is no timeout period after the announcement ends. The moment you let go of the switch, the music begins to ramp up to its original volume.

Note 2: When the manual switch is off, the voice-activated (VOX) control for the paging mic is still operational. Ensure that the PAGING MIC VOX threshold is set accordingly to prevent false triggering of the paging mic input when using PAGING MIC CONTROL switching. Alternatively, turn the PAGING MIC VOX control all the way up (fully clockwise) to defeat the VOX circuit. Note that each zone has its own PAGING MIC VOX control.

Setting the GAIN

When a microphone is connected directly to the paging mic input, the GAIN +40 dB switch should be set in the down position (for a mic-level signal). When

the paging mic is going through an external mixer, sending a line-level signal to the paging mic input, move the GAIN +40 dB switch to the up position (for a line-level signal only).

Adjust the MASTER VOLUME control by pressing the up/down buttons so the meter indicates a level at the “0” mark. With all music sources off, speak into the paging mic with a normal voice. Adjust the PAGING MIC GAIN control with a non-conductive alignment tool so that the meter indication is near the “0” mark. This provides the best signal-to-noise ratio for the mic, and insures that the signal from the paging mic is strong enough to trigger the VOX circuit.

Setting the VOX Threshold

This control determines how strong the signal from the paging mic must be to trigger the VOX circuit, which ducks the program source when an announcement is made. Ideally, the threshold should be set so it is sensitive enough to trigger the VOX circuit as soon as you begin speaking, but not so sensitive as to be triggered by ambient sounds around the microphone. Set the PAGING MIC VOX control to the center position with a non-conductive alignment tool to start. Turn the control counter- clockwise to lower the threshold (increase the sensitivity) if the beginning of announcements are getting clipped off. Turn the control clockwise to increase the threshold (decrease the sensitivity) should you experience false triggering due to ambient noise around the microphone.

Using the EQ

The paging mic has a 2-band equalizer for adjusting the lows or highs on the microphone signal. When the controls are set to “U” (unity), the EQ has no effect on the signal.

Using the Ambient Mic

The ambient mic is an optional accessory (MT-

3100) that is available for the SP1200, which is used to sense the ambient noise level in the room. Set the AMP ADDRESS switch #8 up to enable the ambient mic, otherwise leave the switch down.

The ambient mic provides an “ear” for the micro- processor to gauge the ambient noise in the room and adjust the gain of the paging mic accordingly. When the background noise is relatively quiet, the paging mic gain is at its lowest level. If the background noise is relatively loud, the paging mic gain is at its highest level. If the background noise is some- where in between, the paging mic gain is midway between its lowest and highest preset levels.

SP1200 – 19