When configured for redundancy, both return transmitters are normally active and transmit the combined RF return signal simultaneously. In the event of path failure, continuity of service is accomplished at the headend or the receiver site by switching to the alternate or active return fiber.
Signal levels are adjusted in each return path using Model JXP-* attenuator pads. Units are shipped with a JXP-5 (5 dB) attenuator pad at the input position of each installed transmitter. If only one transmitter is installed, there will be a 15 dB pad at the second transmitter input position to serve as a termination.
DS-SG2-DRT-2X/A
The DS-SG2-DRT-2X/A has two separate RF inputs. The transmitter digitizes these two independent analog 5-42 MHz return-path signals to produce two 1.25 Gbps data streams. These two data streams are then multiplexed to create a single 2.5 Gbps data stream that is then routed to a digital laser for transmission to a corresponding digital return receiver. In conjunction with these transmitters, the node must also be configured with the SG2 Return Path Module/Split (SG2-RPM/S). Return signals from two of the four node ports are fed to one RF input of the transmitter while the remaining two return signals are fed to the second RF input. The signal paths for both inputs are explained in more detail in Section 5, “Operation”.
Signal levels are adjusted in each return path using Model JXP-* attenuator pads. The transmitter gets one of its RF signals automatically when the unit is plugged into its appropriate slot. The second RF signal comes through a special adapter from the adjacent connector, which is normally available for installing a redundant transmitter. Therefore, the units are shipped with two JXP-5 attenuator pads at the input positions.
Ingress control switching is an available option with any return transmitter configuration. If ingress switches are not used, JXP-2 pads are installed in each ingress switch position on the main RF board.
The node can be configured with one or two DS-SG2-DRT-2X/A transmitters, with dual transmitters providing redundancy. The redundancy configuration is explained in more detail in Section 5, “Operation”.
Section 5, “Operation,” also provides detailed information and block diagrams for each series of digital transmitters.