SM1 Series Microphone Instructions
The SM1 is a high quality, 12VDC powered, flush mount, omni-directional, pre-amplified
microphone for use with DRVs, IP cameras, etc. Note- the audio output of the SM1 is jumper
selectable “line level” (0db) or “microphone level” (-30db).
SM1 Microphone Placement.
Do not mount the microphone near air conditioning vents, light fixtures or electrical equipment.
The SM1 should be placed as close as possible to the subject(s) to be monitored. The SM1 is
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 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 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 to the
surface with screws. A single gang electrical box can be used for surface mounting or consider
using an SM1-LE or SM1-LE2 in place of the SM1.
Adjusting the SM1 Gain
The SM1 output level is set by selecting the desired volume range and adjusting the gain control.
The “Volume Range” switch should be set to the “LO” position when using the SM1 with IP
cameras that utilize “microphone inputs” also known as “Mic. Level” inputs. The switch should be
placed in the “HI” position when using IP cameras with “Line level” inputs of DVRs and IP
cameras.
The SM1 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 Hi-Cut/Lo-Cut Jumpers
The normal frequency response of the SM1 microphone is 500-13Khz. When both switched “in”,
The “HI Cut” and “Lo Cut” filters set the SM1’s frequency response to 900-6Khz. Enabling one or
both of the filters is useful when background noise needs to be further reduced and intelligibility of
speech emphasized. We recommend experimenting with the switch settings to achieve the best
result for your application.
