SM1-D Microphone Instructions
The SM1-D is a superior quality, Dynamic, 12VDC powered, unidirectional, surface mount, pre-amplified microphone for
use with DRVs, I/P cameras, etc. Note- the audio output of the SM1-D is “line level” (0db).
SM-D Microphone Placement.
Locate the SM1-D Microphone near the area of interest in the room to be monitored. If the entire room is to be monitored,
locate the SM1-U in the middle of the room. Do not mount the microphone near air conditioning vents, light fixtures or
electrical equipment. The SM1-D should be placed at least five feet away from the subject(s) to be monitored. The SM1-D
is still useable in the range of 15-25 feet but is dependent on the level of background noise in the area. Experimentation in
the environment will determine what distances work best.
Cable Run
Run a 22 gauge, stranded, two conductor shielded cable between the SM1-D microphone and the monitoring device.
Keep the cable run distance under 1,000 feet and away from AC power sources, light fixtures and electrical equipment.
Connect power to the + terminal, the audio signal to the “audio” terminal and ground to the – terminal. The Ground of the
power and audio signal must share a common ground for proper operation.
See Figure 1 for connection diagram.
Mounting
The SM1-D can be surface mounted on ceilings or walls. It is best suited mounted on acoustic ceiling tiles where less
mechanical vibration will be picked up from Air conditioning units etc.
Adjusting the SM1-D Gain
The SM1-D is shipped with the gain set at midrange. If the sound at the “head end” is distorted, rotate the control towards
the – mark (counter-clockwise). If the volume at the “head end” is too low, rotate the control towards the + mark
(clockwise).
Setting the SM1-D Jumpers
The SM1-D microphone has jumper selectable treble boost and limiter circuits. The treble boost circuit when shunted to
the “in” position emphasizes the high frequency sounds that the microphone picks up. This is useful for improving the
sound quality on slow speed tape recordings (VCR time-lapse recordings). The limiter circuit shunted to the “in” position
automatically keeps the SM1-D’s output at a relatively constant level. This eliminates the need for the listener to reduce
the volume control on the amplifier when sounds get louder.
Note: Do not use the SM1-D’s limiter circuit if you are using a tape recorder or other device that uses an AGC or
limiter circuit. Most tape recorders have limiter circuits.
The recommended jumper settings are as follows:
Stand-alone Application
Tape Recorder Application
Limiter “IN”
“OUT”
Treble Boost
“OUT”
“IN”
Caution
It may be against the law to install this microphone kit in certain environments. It may also be against the law to record conversations of
the person(s) being monitored without their knowledge. It is the responsibility of the installation company and end-user to determine if
the application of this product is legal. These laws vary from state to state. If you are not informed on these matters, consult a qualified
attorney or contact the appropriate state agency. A sticker is provided with this kit for the applications where notification must be
posted.
