( ) = Approx RFS input sig in dBm Figure 70.- Probability of bit error.

Figure 71.- Functional block diagram of TMU.

data supplied from the FDS at 8 1/3 or 33 1/3 bps. The high-rate 240-kHz subcarrier was biphase modulated with the coded/uncoded high-rate telemetry data supplied from either the FDS at 2000 bps, the DSS at 2000, 4000, 8000, or 16 000 bps, the RTS at 4000 bps, or the VLC at 1000 or 2000 bps. The subcarrier and data streams were not coherent. The TMU1s contained a block coder capable of encoding high-rate data supplied from the DSS or FDS. A data switch was controlled by command from the CCS and provided the means to bypass the block coder if desired. The TMU provided a one- or two-channel telemetry system which permitted low-rate data (primarily engineering performance monitoring data) to be continuously transmitted to Earth, either separately or in a weighted sum with selected high-rate data (primarily science data). The normal operating modes were numbered mode 0 through mode 6 depending on the presence and source of high-rate data. These modes are summarized in table 22. The selection of the source of high-rate data was determined by the receipt of a command pulse on one of several interface lines with the CCS. The TMU mode logic assured that the TMU was set to mode 0 upon application of power. Interruptions in the 2.4-kHz power of 100 msec or longer caused the mode logic to reset the TMU to mode 0.

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