User manual

Appendix F: Redundant Backup F-9
Moseley SL9003Q 602-12016 Revision G
Receiver Composite Switching
The Starlink Digital Composite requires an external signal router to select the active composite
output. The Broadcast Tools SS 2.1/BNC III switcher/router is shown in Figure F-5 performing
this function. The router selects one of two unbalanced coaxial inputs. In a typical installation it
is rack mounted between the main and standby receivers.
The Main Receiver provides control logic from the RJ45 connector (XFER) on the NMS card for
switching signal the switcher/router. The Main receiver control line (RJ45 pin 6) will be HIGH
(+5V), signifying the Main receiver to be good and router input 1 will be selected. If the Main
receiver fails, the line will go LOW, and input 2 will be selected (the Standby receiver will then
be active).
The Broadcast Tools switcher router is configured internally with DIP switches to operate from
external control. Remove the lid from the router and switch the DIP Switch 5 – 6 to the ON
position. Replace the lid.
Also the Broadcast Tools SS2.1 BNCIII switcher/router has an impedance selection jumper that
must be taken into consideration. By the default the router places a 75 ohm resister in series
with the common output. We suggest installing jumper JP1 which bypasses this resister and
sets the impedance to 0 ohms.
The only time it may be desirable to leave this jumper out is if there is a long length of cable
between the router and the exciter and frequency response (and stereo separation) are
adversely affected by cable capacitance. In this case the exciter must be terminated in 75 ohms.
This will lower the composite level by 6 dB which may lead to other complexities.
The transfer control cable is available from Moseley for this configuration (203-12416-01),
although a cable can be made from a shielded RJ-45 (Black Box p/n EVNSL60-0006). This is a
6 foot cable that can be cut, and the ends tinned to provide the RX XFER OUT signal (RJ45 pin
6) for the indicated connection. Be sure to maintain the shield performance by connecting to
ground. The high RF levels in typical STL receiver environments can cause problems.