CM Expander Unit

Service Observing ExpanderModel CMX-300
Discontinued-No Replacement

Expands the CM-30 in increments of 30 lines

User Guide (pdf)
Product Brochure (pdf)

Each CMX-300 provides an additional 30 lines to the basic 30 lines provided by the CM-30. You may add up to two Model CMX-300s which will allow one Observer to monitor up to 90 lines. All the standard features of the CM-30 are maintained when using the CMX-300. Installation is easy (see User Guide).

You can add the CMX-300 to an existing CM-30 installation without disrupting the existing service. The CMX-300 is controlled by the CM-30: simply connect the additional lines you want to monitor and you’re ready to start.
No extra power supply unit is required. The CMX-300 gets its power from the CM-30.

When your system needs to grow beyond the 30 line capacity of the CM-30, you can expand quickly and efficiently with the CMX-300. It will allow you to expand your system in increments of 30 lines per unit, up to a total of 90 lines.
If the size of your organization already exceeds 30 lines, the combination of the CM-30 and CMX-300 is your solution.


  • 30 line capacity
  • Expands the CM-30 in increments of 30 lines per unit up to 90 lines
  • Compatible with analog Centrex, PBX or Key System lines
  • Connectorized interface
  • Can be wall mounted


Ordering Information

CMX-300 CM-30 Expansion – 30 lines


Min Typical Max Unit
Breakdown Volts
Observed lines to ground 1000 VDC
Operating Temperature 32 122 °F
0 50 °C
Humidity (non-condensing) 95 % RH

Two A25B or equivalent 25 pr. female connector cables

Apparatus cabinet, relay rack or backboard

Dimensions (HxWxL)
Unit: 9.25” x 5.40” x 1.58” (23.5 x 13.7 x 4 cm)
Packaged: 10.75″ x 6.375″ x 3.375″ (27.3 x 16.2 x 8.6 cm)

Shipping Weight
1.98 lbs (898 grams)


Approval Number

DOC CS03 350 3518 A
CSA C22-2 No. 225-M90 LR 91817
FCC Part 68 FCNCAN-61252-PX-N
UL 1459-2 D0292442DBC

Related Products

CM-30  [Back to TOP]