Lectrosonics FM870 - Manual (Page 7)

M170 SERIES TRANSMITTERS cont’d
The BATTERY used in the transmitter should be a 9 Volt alkaline battery which will provide up to 15 hours
or more of operation. These are available almost anywhere. Carbon zinc batteries, even if marked "heavy
duty" or "super heavy duty", will only operate up to 4 hours. Make sure "alkaline" is marked on the battery.
The BATTERY INDICATOR will light when the transmitter is turned on and will stay lit as long as the
battery is good. If the battery is low, the battery indicator will grow dim and finally go out. Even after the
indicator goes out, there may still be up to an hour or more of use remaining. When the battery is too low
for proper operation, the sound from the wireless system may be intermittent or totally absent. When the
transmitter is first turned on, it may require several minutes to get a "true" battery reading. For example,
if a dead battery were not used for a day or so, and then was used in the M170, it might indicate for a
minute or so that it was good. This is just like the "dead" batteries in a flashlight that will shine brightly for
a few minutes then rapidly go dim.
If you are experiencing short battery life (six hours or less), you are probably not using alkaline batteries.
In most cases, we have found short battery life to be due to the use of batteries that are not alkaline.
The MIC JACK is a threaded, locking, micro jack that supplies phantom power for electret microphones
such as the M140 lavalier model and the headset models. Insert the microphone plug into this jack and
rotate it clockwise to lock it. The microphone cord is the antenna for the transmitter. The standard 3-pin
XLR CONNECTOR is designed for best performance with standard, balanced, 50 to 600 Ohm impedance
microphones, although it will work with high impedance microphones. If your microphone has selectable
impedance, set or wire it for 150 or 200 Ohms, or set it to the "low impedance" position.
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