SM1-C Microphone Instructions
The SM1-C is a high quality, 12VDC powered, remote element, omni-directional, pre-amplified microphone 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).
SM1-C Microphone Placement.
Locate the SM1-C Microphone near the area of interest in the room to be monitored. If the entire room is to be
monitored, locate the SM1-C in the middle of the room. Do not mount the microphone near air conditioning vents,
light fixtures or electrical equipment. The SM1-C should be placed at least five feet away from the subject(s) to be
monitored. The SM1-C 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-C 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
In covert applications, the SM1-C interface box can be placed out of site, and the microphone element can then
be placed into a hole drilled into a drop in ceiling tile, etc. The SM1-C can also be mounted on a ceiling with the
microphone element left hanging down to close the distance between the microphone and the subject.
Adjusting the SM1-C Gain
The SM1-C 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-C with I/P cameras that
utilize “microphone inputs” also know as “Mic. Level” inputs. This sets the maximum gain of the SM1-C’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-C’s pre-amp to x196.
The SM1-C 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-C Hi-Cut/Lo-Cut Jumpers
The normal frequency response of the SM1-C microphone is 500-13Khz. When both jumpered “in”, The “HI Cut”
and “Lo Cut” filters set the SM1-C’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 jumper settings to achieve the best acoustic result for your application.
Available from A1 Security Cameras
www.a1securitycameras.com email: sales@a1securitycameras.com
