OTEK’s recently developed Model MBWC, or multi-band 2-way wireless controller, supports four universally acceptable RF bands (315 MHz, 433 MHz, 868 MHz and 915 MHz) without changing hardware or firmware. The controllers use OTEK’s MBTR radio modem (see the figure), which is FCC-approved for certain bands and power. The controllers are factory configured for a specific band and output power level to match a specific country’s requirements. In the future, a 2.4 GHz band operating with the ZigBee protocol will be offered.

According to Otto Fest, president of OTEK, the most popular applications are for hazardous locations where the units preclude the need to breech physical barriers for cabling. One setting where this advantage is exploited is in offshore drilling. While the MBWC is not rated for military applications, it is ruggedized.

In such extreme applications, the units are often situated in harsh RF environments that cause reflections, attenuation, and multipath effects. Fest states that the MBWC uses frequency hopping and retransmission to improved the robustness of the RF link.

There are also two modes to warn of a failed link. In the first, the transmitter warns when the receiver has failed to acknowledge reception. In the second, the receiver has a watchdog timer that signals an alarm when no signal has been received from the transmitter.

The units can supply up to 6 mW of transmit power, providing a line-of-sight range of 1000 feet. They are FCC-licensed for 902 MHz to 928 MHz (frequency hopping) and 315 MHz/433 MHz (on/off control). Analog accuracy of the I/O signals is + 0.1%.