SM1-PH Microphone
Pre-Amplifier Instructions
The SM1-PH is a high quality, 12V-24VDC powered, pre-amplified, pin hole style microphone designed to
connect to DRVs, I/P cameras, etc. Note- the audio output of the SM1-PH is switch selectable “line level”
(0db) or “microphone level” (-30db).
Microphone
Plug the ML1-PH microphone into the “mic in” jack of the SM1-PA pre-amplifier. Do not mount the ML1-
PH microphone near air conditioning vents, light fixtures or electrical equipment.
The ML1-PH microphone should be placed as close as possible to the subject of interest. The ML1-PH
microphone is useable in the range of 3-25 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-PH pre-amplifier 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-PH is designed to be mounted in a ceiling tile or wall. See figure 2.
Adjusting the SM1-PH Gain
The SM1-PH 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-PH with I/P cameras
that utilize “microphone inputs” also known as “Mic. Level” inputs. This sets the maximum gain of the
SM1-PH’s pre-amp to x14. The switch 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-PH’s pre-amp to
x196.
The SM1-PH 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-PH Hi-Cut/Lo-Cut Switches
The normal frequency response of the SM1-PH microphone is 500-13Khz. When both switched “On”,
The “HI Cut” and “Lo Cut” filters set the SM1-PH’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.
Содержание SM1-PH
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