The ACU3 Automatic Changeover Unit provides a control and command capability for dual redundant transmission systems. It is particularly suited to remote transmitter site installations, where it may take some time for an engineer to arrive and switch over to reserve equipment. The ACU3 will automatically switch between main and reserve chains to keep the radio station “on-air”.

The ACU3 contains a coaxial relay which is capable of switching the RF output of either chain (up to 100W at band II frequencies) to the antenna system or a high power amplifier. External relays may be driven for switching of higher powers.

Eight fault input lines are provided to monitor system parameters, for example: forward/reflected power, PLL lock and operation of the audio chain components such as the stereo encoder and deviation limiter. Control can be applied to the main/reserve chain by connection to the open collector mute outputs. A change-over delay is implemented to overcome erroneous switching during power “glitches”. All eight fault lines are mirrored to an external telemetry interface. Control inputs/outputs are provided via this interface to allow the selection of either main or reserve transmitter, or to completely shut down the system.

The front panel A/Auto/B switch provides local control, and allows system testing. Quick-view status monitoring, using LEDs, is provided for on-site monitoring of the active chain and to show whether the system is being muted by an external control signal.

The ACU3 is built to the same very high standards that all sbs transmission systems meet and will give many years of trouble free service, with no routine maintenance being required. It will operate unattended and give full peace of mind, by ensuring that the reserve chain takes over when really needed.

Special Features.

Comprehensive monitoring and control of main / reserve transmitters

Capable of switching up to 100W internally or higher powers using an external relay

Also suitable for use with STL transmitter products

Specifications

RF inputs 2x N type (100W max - higher with external co-ax relay)

RF output N type (100W max - higher with external co-ax relay)

Useable frequency range DC - 1GHz

Insertion loss 0.14dB at 100MHz

Minimum return loss Better than 25dB, 88 - 108MHz (Active input to output)

External relay drive 24V, 250mA maximum (regulated)

Fault inputs “Low” for system normal

Fault detection time User adjustable (5-40 secs.)

Fault monitor outputs Open collector, “High” for system normal

Power supply 100/115/230Vac ± 10%, 50/60Hz

Power consumption < 30VA

Temperature (operating) -20C to 45C

Humidity (operating) < 90% RH, non condensing

Dimensions 44mm high (1U) x 443mm wide x 280mm deep (inc. connectors)

Weight 2.3kg