SM1-U Microphone Instructions
The SM1-U is a high quality, 12VDC powered, unidirectional, flush mount, 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).
SM-U Microphone Placement.
Locate the SM1-U 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-U should
be placed at least five feet away from the subject(s) to be monitored. The SM1-U 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-U 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-U 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-U to
the surface with screws. For surface mounting, use a single gang electrical box.
Adjusting the SM1-U Gain
The SM1-U 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-U with I/P
cameras that utilize “microphone inputs” also know as “Mic. Level” inputs. This sets the
maximum gain of the SM1-U’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-U’s pre-amp to x196.
The SM1-U 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-U Hi-Cut/Lo-Cut Jumpers
The normal frequency response of the SM1-U microphone is 500-13Khz. When both jumpered
“in”, The “HI Cut” and “Lo Cut” filters set the SM1-U’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: [email protected]
