SM1-TR Microphone Instructions
The SM1-TR is a stainless steel, tamper resistant, high quality, 12VDC powered, flush mount,
omni-directional, pre-amplified microphone with a for use with DRVs, I/P cameras, etc. Note- the
audio output of the SM1-TR is “line level” (0db).
SM1-TR Microphone Placement.
Locate the SM1-TR Microphone near the area of interest in the room to be monitored. If the entire
room is to be monitored, locate the SM1-TR in the middle of the room. Do not mount the
microphone near air conditioning vents, light fixtures or electrical equipment. The SM1-TR should
be placed at least five feet away from the subject(s) to be monitored. The SM1-TR 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-TR 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-TR can be surface or flush mounted on ceilings or walls. For flush mounting, cut a 2 ¼”
by 2 ¾
“ hole in the wall or ceiling tile to allow room for the circuit board and mount the SM1-TR to
the surface with screws. A single gang electrical box can be used for surface mounting or
consider using an SM1-TR-LE in place of the SM1-TR.
Adjusting the SM1-TR Gain
The SM1-TR 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-TR Jumpers
The SM1-TR microphone has jumper selectable treble boost and peak limiter circuits.
The limiter circuit lowers the gain of the microphone preamplifier, preventing it from clipping
during very loud sound intervals. During normal audio levels, the limiter circuit has no affect on
the audio signal and there won’t be any observable result in performance. If there will be periods
of high volume in your application, jumper the limiter “in”. Note-as the gain control is decreased,
the limiter will have less affect on the pre-amplifier during loud sound intervals.
The Treble boost circuit emphasizes the high frequencies of the pre-amplifier. Jumpering treble
boost to the “in” position will result in improved pick up of faint conversations such as whispers.
Note however, when the treble boost is on, background and amplifier noise will increase as well.
