These units monitor the acoustics within a room, and then transmit data via an existing telephone line at undetectable levels. Note that the INT-A038-1 uses an analog channel, while the INT-A038-2 uses a digitally encrypted channel.
The units are designed as printed circuit boards (PCBs), protected by plastic coverings. Both come equipped with a telephone line connection, as well as a connection for an external mic. Connecting to telephone lines is done through a parallel connection.
The receiver for these units features a sturdy metal case for protection, has built-in jacks for connecting a headset, an external recording device, telephone cables and an external PSU. The receiver provides volume control, on/off functionality, battery condition and the presence of an external PSU. Note that the INT-A038-2 unit offers Delta modulation automatic decryption, and can be combined with the commutating device INT-A038-2 Commutator intended for gain control and data transfer between lines and avoid the PBX.
No interference is created in the phone line by connecting either transmitter, and the line can be used as normal when the transmitter is installed.