power supply is providing power to the intercom circuit. In addition to power, it’s expected that the external power supply will also provide the required 200 ohm ter- minating impedance to both pins 2 and 3.
When switch 1 is in its on (up) position the Model 46 will provide a 30 volt, 300 mil- liamperes maximum source of DC power to pin 2 of the 2-wire PL intercom connec- tors. The Model 46 will also provide 200 ohm terminating impedances for both pin 2 and pin 3 of the party-line connectors. The DC power and termination capabili- ties allow direct powering of dual-chan- nel intercom belt packs, such as the RTS BP325. In addition, listen-only belt packs, such as the Model 34 from Studio Tech- nologies, Inc. can be directly connected. There’s also no problem connecting single-channel intercom belt packs or user stations.
2-Wire Nominal Audio Level
DIP switch 2 allows adjustment of the nominal audio level for the two 2-wire party-line channels associated with inter- face 1. When the switch is in its off (down) position the nominal level is –14 dBu. This level is compatible with intercom belt packs from manufacturers such as Clear- Com. When the switch is in its on (up) position the nominal level is –10 dBu. This setting is appropriate when belt packs from RTS, such as the BP325, or listen- only talent amplifier units from Studio Technologies, Inc. are connected. For best Model 46 performance it’s important that the 2-wire nominal level selection be made correctly.
4-Wire Nominal Audio Level
DIP switches 3 and 4 are used to config- ure the nominal level of the input and out- put circuitry associated with interface 1’s two 4-wire input and output connections. Four level settings are available: 0, +4, +6, and +8 dBu. Prior to setting these DIP switches it’s important to determine the nominal audio level of the equipment con- nected to the Model 46’s 4-wire input and outputs. This may take a little investigation but is important for obtaining the best pos- sible Model 46 performance.
The 0 dBu setting is provided specifically for use when a Model 46 is interconnected with a Clear-Com matrix intercom system. The +4 dBu setting is appropriate when standard audio lines with “+4” nominal levels are interconnected. The +6 dBu setting can be appropriate when intercon- necting with equipment manufactured in Europe, such as the digital matrix intercom systems from Riedel. The +8 dBu setting is provided specifically when interconnect- ing the Model 46 with audio signals asso- ciated with an RTS ADAM-series of matrix intercom system. This includes the related RVON-I/O unit.
When DIP switches 3 and 4 are in their off (down) position the nominal level is set for 0 dBu. When switch 3 is on (up) and switch 4 is off (down) the nominal level is +4 dBu. When switch 3 is off (down) and switch 4 is on (up) the nomi- nal level is +6 dBu. When both switches 3 and 4 are in their on (up) position the nominal level is configured for +8 dBu.
