SM1-T Microphone Instructions
The SM1-T is a high quality, table top, 12VDC powered, flush mount, 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-T Microphone Placement.
Locate the SM1-T Microphone in the middle of the room to be monitored such as on a conference
table. Do not place the microphone near light fixtures or electrical equipment. The SM1-T should
be placed at least five feet away from the subject(s) to be monitored. The SM1-T 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 and Connection
Remove the 4 screws holding the bottom cover on and connect the wires as shown in figure 1.
Run a 22 gauge, stranded, two conductor shielded cable between the SM1-T 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.
Adjusting the SM1-T Gain
The SM1-T 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-T with I/P
cameras that utilize “microphone inputs” also know as “Mic. Level” inputs. This sets the
maximum gain of the SM1-T’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-T’s pre-amp to x196.
The SM1-T 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-T Hi-Cut/Lo-Cut Jumpers
The normal frequency response of the SM1-T microphone is 500-13Khz. When both jumpered
“in”, The “HI Cut” and “Lo Cut” filters set the SM1-T’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]
