# Cautionary Note about Interfacing to PBXs

Caution: Must be using an Analog Phone Line

Some PBX systems are either partially or entirely digital circuitry. That is, voice and signaling information is converted to a digital representation. Voice information arriving at the PBX from the outside is converted from analog to digital. Voice information leaving the PBX to the outside is converted from digital to analog. Phone sets within a digital system may be interfaced by digital signals only. In such systems it may be difficult, but usually not impossible, to obtain a standard analog phone line to use in interfacing devices such as the Catalyst RTU. It may be necessary to contact the vendor of your PBX system for information on the addition of analog lines.

Warning: Digital Phone Lines Can Cause Damage

Caution is advised. Some telephone lines within digital PBXs present voltages that can be dangerous to RACO equipment. If you were attempting to interface a Catalyst inside of a PBX, it would be a good practice to have the phone line you intend to use, checked for "unusual" voltages and signals.

With few exceptions, if you can get a standard telephone set to work on a PBX line, then you will be able to make the Catalyst work as well.