MJ-4 Communications Module 
  35 
10 Specifications 
This section contains the MJ-4 Communications Module specifications. Contained in this section are the parameters 
for both the fiber optic and RS-232/485 interfaces. The data provided in the fiber optic section was obtained using 
62.5/125 µm cable. Typical, maximum, and minimum lengths are given for normal and long range cable lengths. 
Except for the maximum and minimum parameters, the numbers provided are for room temperature. The maximum 
and minimum lengths are for temperature extremes. 
10.1 Physical Dimensions 
Height  8.4 inches   ( 21.34 cm ) 
Width  2.89 inches (   7.34 cm ) 
Depth  2.84 inches (   7.21 cm ) 
10.2  Fiber Optic Link Interface Specifications 
Transmitter  Jumper J12 In  Jumper J12 Out 
Maximum Output Power  -13.0 dBm (Long Range)  -16.0 dBm (Normal Range) 
Typical Output Power  -16.0 dBm (Long Range)  -19.0 dBm (Normal Range) 
Minimum Output Power  -20.0 dBm (Long Range)  -23.0 dBm (Normal Range) 
Numerical Aperture  0.49   
Optical Port Diameter 
290 µm 
 
Receiver 
 
Peak Input Power Logic Level Low  -24.0 dBm Min to -9.2 dBm Max   
Peak Input Power Logic Level High  -40.0 dBm Max   
System 
 
Wavelength  820 nanometers (nominal)   
Connector Type  ST   
Fiber Type 
Glass 62.5/125 µm, 5dB/m 
 
Data Rate  5 Mbaud (design)  19.2 Kbaud (tested) 
Maximum Optical Power Budget  11 dBm (Long Range)  8 dBm (Normal Range) 
Typical Optical Power Budget  8 dBm (Long Range)  5 dBm (Normal Range) 
Minimum Optical Power Budget  4 dBm (Long Range)  1 dBm (Normal Range) 
Link Lengths 
 
Maximum Link Length  2.2 km (Long Range)  1.6 km (Normal Range) 
Typical Link Length  1.6 km (Long Range)  0.6 km (Normal Range) 
Minimum Link Length  0.8 km (Long Range)  0.2 km (Normal Range) 
Operating Temperature Range  -40ºC to +85ºC (excluding cable)   
 
10.3 RS-232/RS-485 Interface Specifications 
Parameter RS-232  RS-485 
Data Rate (maximum)  19200 baud  19200 baud 
Distance (maximum)  50 ft  4000 ft 
Nodes (maximum)  72  32 
Isolation  500 VAC, 1 minute  500 VAC, 1 minute