The RB-OA3 is a 1U rack-mount unity gain antenna switcher, capable of switching three stereo pairs between three studios. Each studio can control the transmission path as well as two peripheral paths for equipment such as a codec or hybrid, and there is also a "Last Studio to Offer" bus, allowing continuous and uninterrupted broadcasting from any multi-studio radio network. A "sustain" mode allows a sustain system, such as a PC automation system, to control the broadcast. Multiple RB-OA3 units can be connected together to switch more studios or more stereo pairs.

- Controls offer/accept switching for 3 studios.
- Switches 3 bidirectional stereo channels, e.g. studio output, codec clean-feeds, telco feeds.
- Has a transformer balanced stereo mix input, e.g. for playout system.
- Continuity mode allows switching to/from a PC playout system.
- Latching relay switching maintains the transmission path intact on power fail.
- Can be expanded to switch 6 stereo channels between 5 studios.


Switching is accomplished using relays, except for the "last studio to offer" which is switched by an analogue switch. The transmission path is switched using latching relays. This means that in the event of a power failure to the unit, the transmission path will remain selected.

All studios are connected using 25-way D-type connectors for electronically balanced audio signals, and control is via 15-way D-type connectors, connecting to an external control unit such as the Sonifex S2-MTBS mixer control panel. A transmission mix connection is included to mix generic audio to all studios in the transmission path. This could be used for jingles or commercials for example. The RB-OA3 also allows for the control of a shared profanity delay by all connected studios.

Each studio has the ability to offer the transmission. Once offered, the transmission is sent to the other studios via the "last studio to offer" bus. The next scheduled station can then fade in the transmission and accept at the appropriate time, meaning that the transmission can be continuous.

The "sustain" mode can be used to control an automated studio, such as a night-time music system. In this case, control of the station will pass to the automated system by holding down the Offer button for several seconds, predetermined by a calibration routine. This will select the sustain studio, defined as studio three, which will immediately offer control to all remaining studios. Any studio can then accept to resume orthodox broadcasting.

The RB-OA3 can be expanded to switch between up to 5 studios or up to 6 stereo pairs by connecting multiple units together via RJ45 serial connections. With the addition of a single unit, expansion in "studio" mode allows 2 additional studios to take control of the transmission path and additional equipment. If expansion is done in "bus" mode, then three additional stereo channels can be added. 4 RB-OA3 units can be connected together to switch 6 stereo pairs between up to 5 studios.

Modes are configured by DIP switch settings, on the rear of each unit. Two DIP switches control the unit ID and there are two switches which decide between "studio" and "bus" modes. A master unit, defined by a preset ID, handles all communication between all units.