SMA1-MPEA Interface Instructions
The SMA1-MPEA is a single channel, two way audio Interface box designed to be used with ETS speaker / microphones
(OR separated speakers and pre-amplified microphones) and Power Over Ethernet IP cameras. It contains a 10 Watt
speaker power amplifier to drive an 8 Ohm speaker and an ETS microphone interface. The SMA1-MPEA can be
connected to a “microphone” or “line” level input and “line level” output of a POE IP camera. Note- this equipment is
intended for use with camera or VMS software that has a PTT (push to talk) half duplex option for two way audio. If your
software does not support this mode you may get acoustical howling feedback.
SMA1-MPEA location and power
The SMA1-MPEA should be located within 6’ of the IP camera. The SMA1-MPEA has 2 modes of operation. Mode 1
allows the SMA1-MPEA to be connected in between the network switch and the IP camera. In mode 1, a PoE plus
network switch is recommended. In mode 2, the SMA1-MP can be connected to its own PoE port on the network switch
for power only. A separate network cable is then run to the camera from the network switch. PoE plus is not needed for
mode 2.
Note- in mode 1 the PoE sense resistor should be switched “OUT” and for mode 2 it should be switched
“IN”.
Microphone / Speaker Placement.
Avoid mounting the speaker
and
microphone near air conditioning vents, light fixtures or electrical equipment. The
speaker
and
microphone
should be placed as close to the subject(s) as possible. 5 to 10 feet is ideal. The speaker
and
microphone are still useable in the range of 15-25 feet in public address applications but is dependent on the level of
background noise in the area. Experimentation in the environment will determine what distances work best.
Microphone and Speaker Cables
Run a 22 gauge, stranded, two conductor shielded cable for the microphone up to 1000’ long. The speaker cable should
be 18guage cable up to 300’ long. Keep cables away from electrical equipment and light fixtures.
Adjusting the microphone “gain” and SMA1-MPEA output “level” controls
If the SMA1-MPEA will be plugged into a “microphone level” input of an IP camera, set the microphone gain slightly
clockwise (or 1/4 of a full turn) from full counter-clockwise. Then use the “level control” on the SMA1-MPEA to set a
volume that produces an acceptable audio level at the head end.
If the will SMA1-MPEA be used with a “line level” microphone input, turn the gain control of the SM1 to 3/4 full clockwise
and adjust the level control on the SMA1-MPEA to produce the clearest audio level at the head end.
Adjusting the speaker volume
Adjust the audio input level for an acceptable volume level on the connected speaker / microphone. If a decent amount of
volume cannot be achieved, place speaker gain range switch in the “High” position.
SMA1-MPEA Mode switch:
The SMA1-MPEA supports Both Modes A and B of IEEE802.3af POE. The SMA1-MPEA is
pre-configured for the most common use of the “end point” POE IEEE802.3af standard (mode A). If the power LED does
not illuminate in this position, try the mode B position (mid span).
