Installation Instructions

SM4 Switcher / Mixer Instructions
The SM4 is a 4 single channel, one way “listen only” switcher / mixer base station for use with all ETS SM1 series
microphones. The SM4 can be used independently or with a CCTV system. The SM4 also easily connects to recording
equipment such as DVRs, linear time-lapse VCRs and audio tape recorders. Note the audio input / output signals of the
SM4 are “line level” (0dbm).
Recorder switch
If the SM4 will be used with a recorder of some type, place the recorder switch in the “IN” position. In this position, both
live audio and playback audio can be heard through the SM4’s internal speaker. In stand alone applications where there is
no recorder or no need to playback recordings, place the recorder switch in the “OUT” position.
Headphone jack
Plug in a set of 3.5mm stereo headphones for private listening. The internal speaker of the SM4 will be automatically
disabled until the headphones are unplugged.
Switcher / mixer mode.
To switch the SM4 between the “1 of 4” mode and the “mixer mode”, press and hold the CH1 button for 5 seconds. In the
“mixer mode”, all channel lights will turn on. In the “1 of 4” mode, all channel lights will go out. The SM4 will remember the
last setting and channels selected in either mode.
SM1 Microphone Placement.
Locate the SM1 microphone near the area of interest in the room to be monitored. If the entire room is to be monitored,
locate the SM1 in the middle of the room. Do not mount the microphone near air conditioning vents, light fixtures or
electrical equipment. The SM1 should be placed at least 5 feet away from the subject(s) to be monitored. The SM1 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 SM4 mixer/amplifier and the SM1 microphones.
Keep the cable run distance under 500 feet and away from AC power sources, light fixtures and electrical equipment. 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. For surface mounting, use a
single gang electrical box.
Adjusting the SM1 Gain
The SM1s are shipped with the gain set at midrange. Adjust the control + or – for maximum clarity. If the sound at the
amplifier is distorted, rotate the control towards the – mark (counter-clockwise). If the volume at the amplifier is too low,
rotate the control towards the + mark (clockwise).
Setting the SM1 Jumpers
The SM1 microphone has jumper selectable treble boost and limiter circuits. The treble boost circuit when shunted to the
“in” position emphasizes the high frequency sounds that the microphone picks up. This is useful for improving the sound
quality on slow speed tape recordings (VCR time-lapse recordings). The limiter circuit shunted to the “in” automatically
keeps the SM1’s output at a relatively constant level. This eliminates the need for the listener to reduce the volume control
on the amplifier when sounds get louder.
Note: Do not use the SM1’s limiter circuit if you are using a tape recorder or other device that uses an AGC or
limiter circuit. Most tape recorders have limiter circuits.