User's Manual
System 9 Installation and Operation 
7
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For future reference, please record your system information here. The serial number 
appears inside the battery compartment in each transmitter, and on the bottom of each 
receiver.
  Receiver
  Model ATW-R900a  Serial Number
  Transmitter
  Model ATW-T90  Serial Number
1a or 2a
OVERALL SYSTEM
Operating Frequencies  VHF highband, 169 MHz to 172 MHz
Modulation Mode   FM
Maximum Deviation   ±10 kHz
Dynamic Range   ≥90 dB (A-weighted), typical
Total Harmonic Distortion  <1.5% (at 1 kHz, ±10 kHz deviation)
Operating Range   200' (60 m) typical
Open range environment with no interfering signals
Operating Temperature Range  40° F (4° C) to 110° F (43° C) 
Battery performance may be reduced at  
    very low temperatures
Frequency Response  80 Hz to 13 kHz
RECEIVER
Receiving System  Non-diversity, single-channel, 
    dual antenna system
Image Rejection   50 dB minimum
RF Sensitivity  20 dBuV at 60 dB S/N ratio 
    (50 ohms termination)
Normal Output Level   
XLR, balanced:  350 mV (1 kHz modulation, 10 kHz  
  deviation, 100k ohm load)  
1
/4" (6.3 mm), unbalanced:  700 mV (1 kHz modulation, 10 kHz 
  deviation, 100k ohm load)
Power Supply   100-240V AC (50/60 Hz) to 12V DC .5A  
    (center positive) switched mode external 
    power 
supply
Dimensions  7.48" (190.0 mm) W x 1.82" (46.2 mm) H x  
    5.06" (128.5 mm) D 
Net Weight  12.0 oz (337 grams)
Accessory Included   Power supply
UNIPAK
®
 TRANSMITTER
RF Output Power  10 mW
Spurious Emissions   Following federal and national regulations
Input Connection  Four-pin Locking Connector 
    Pin 1: GND, Pin 2: INST INPUT, 
    Pin 3: MIC INPUT, Pin 4: DC BIAS +9V
Batteries (not included)  Two 1.5V AA
Battery Life  8 hours (alkaline) 
    Depending on battery type and use pattern
Dimensions  2.76" (70.2 mm) W x 4.08" (103.7 mm) H  
    x 0.98" (24.9 mm) D
Net Weight (without batteries)  2.8 oz (80.0 grams)
HANDHELD TRANSMITTER
RF Output Power  10 mW
Spurious Emissions   Following federal and national regulations
Batteries (not included)  Two 1.5V AA
Battery Life  8 hours (alkaline)
    Depending on battery type and use pattern
Dimensions  9.91" (251.8 mm) long, 
    2.11" (53.5 mm) diameter
Net Weight (without batteries)  9.2 oz (260 grams)
Accessory Included   AT8456a Quiet-Flex
™
 stand clamp
†
  In the interest of standards development, A.T.U.S. offers full details on its test methods to  
  other industry professionals on request.
System Operating Frequencies
System Operating Frequencies
Each transmitter/receiver system operates on a choice of four switch-
selected frequencies. Available frequencies are shown below. All 
frequencies may be combined for up to 4 simultaneous operating 
channels. 
Traveling frequencies normally work anywhere in the USA and Canada. 
Not all frequencies available in all areas outside the US. Please check 
with local regulations.
System 9 Operating Frequencies/Channels
  Channel  Frequency – MHz  Frequency Code
  1  169.505  T2
  2  170.245  T3
  3  171.045  T5
  4  171.905  T8
RF Interference
Please note that wireless frequencies are shared with other radio ser
-
vices. According to Federal Communications Commission regulations, 
“Wireless microphone operations are unprotected from interference 
from other licensed operations within the band. If any interference is 
received by any Government or non-Government operation, the wireless 
microphone must cease operation...”
If you need assistance with operation or frequency selection, please 
contact your dealer or the Audio Solutions at Audio-Technica U.
S.
Extensive wireless information also is available on the A-T Web site at 
www.audio-technica.com.








