SM1-P Microphone Instructions
The SM1-P is a high quality, Universally powered, flush mount, omni-directional, pre-amplified microphone with enhanced
features for use with DRVs, I/P cameras, etc. Note- the audio output of the SM1 is jumper selectable “line level” (0db) or
“microphone level” (-30db). The ‘E’ version of this microphone is powered by 12-24Vdc only.
SM1 Microphone Placement
Locate the SM1-P Microphone near the area of interest in the room to be monitored. If the entire room is to be monitored,
locate the SM1-P in the middle of the room. Do not mount the microphone near air conditioning vents, light fixtures or
electrical equipment. The SM1-P should be placed as close as possible to the subject(s) to be monitored. The SM1-P is
still useable at distances of up to 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-P 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. If
you are connecting the SM1-P to an ETS product, connect power to right-most power terminal of the SM1-P and ground
to the ground terminal. The Ground of the power and audio signal must share a common ground for proper operation.
See Figure 1 for connection diagram.
External Power Source
The SM1-P can be independently powered from any voltage source in the ranges of: 9-42VAC and 12-60VDC. For DC
inputs the SM1-P is not polarity sensitive. You may connect or – of the power source to either of the two power
terminals without damaging the microphone.
See Figure 2 for connection diagram.
Mounting
The SM1-P 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-P to the surface with screws. A single gang electrical box
can be used for surface mounting or consider using an SM1-PLE in place of the SM1-P.
Adjusting the Lo-Cut and Hi-cut filters
The SM1-P’s high and low frequency response can be trimmed to reduce background noise. If you are primarily interested
in capturing conversations and want to reduce air conditioning and other noises, rotate both controls (hi-cut and lo-cut) to
just short of full clockwise. Some experimentation may be required to achieve the best results for a given environment.
Adjusting the Automatic Gain Control
The SM1-P features automatic control of gain. This is useful for environments where it is anticipated that sound levels will
range from quiet to loud. This prevents the end user from having to constantly readjust the volume of the base station to
the audio environment and to reduce the possibility of pre-amplifier clipping (distortion). The best way to set this control is
to adjust it to a comfortable volume level (on an ETS base station or PC monitor speakers) when the loudest sounds are
present and constant. Turning the control CW will increase the amount of gain reduction during loud sound intervals. If the
sound is reduced too much during loud sounds, turn the control CCW a small amount and experiment until a comfortable
medium is found.
Adjusting the SM1-P Volume
The SM1-P output level is set by selecting the desired volume range and adjusting the gain control.
The “Volume Range” jumper should be set to the “LO” position when using the SM1-P with I/P cameras that utilize
“microphone inputs” also known as “Mic. Level” inputs. This sets the maximum gain of the SM1-P’s pre-amp to x14. The
jumper should be placed in the “HI” position when using I/P cameras with “Line level” inputs of DVRs and I/P cameras.
This sets the maximum gain of the SM1-P’s pre-amp to x196.
The SM1-P is shipped with the Volume 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). Note- the SM1-P output signal can be used to drive a microphone level input (-60db) of a DVR or I/P camera
by turning the volume all the way down (full CCW) and then CW a small amount.
