BusinessPhone Communication Platform 6.0
System Description ASB 150 02 > Hardware

## Add-on equipment

#### Thermometer

Up to three external temperature sensors, RPM 603 339/1, can be connected to CPU-D_
(CPU-D5 supports only one) and the AUX_-board. Only one temperature sensor is displayed on the telephone set.

#### Excess voltage protection

The boards of the PBX are furnished with "secondary" excess voltage protection on the line inputs. For more difficult external conditions a primary excess voltage protection should be mounted. Refer to the “Installation Instructions” for suitable precautions. Main distribution frame SXK 106 4139/1 has room for this primary protection.

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