The TR 502 Tracking Generator operates with the 7L13 or 7L12 Spectrum Analyzer to provide a calibrated rf signal for swept frequency applications from 100 kHz to 1.8 GHz. The output frequency of the TR 502 can be adjusted to track the spectrum analyzer frequency within 10 Hz. The TR 502, a two-wide unit compatible with the TM 500 Modular Series instruments, is normally used with the TM 503 (Option 07) Power Module. This permits the optional use of a digital counter such as the DC 508A with Option 07. A bright dot, on the spectrum display, identifies the frequency location on the sweep that is indicated by the counter. Higher range counters to 1.8 GHz can be used by connecting their input to the TR 502 AUX RF OUT connector. The TR 502 Tracking Generator is a two wide plug-in unit for the TM 500-Series (Option 7) Power Modules. It operates with the 7L13 or 7L12 Spectrum Analyzer to provide a constant, level-calibrated rf signal source, that precisely tracks the spectrum analyzer input frequency from 100 kHz to 1.8 GHz. Signal output level is calibrated and adjustable from 0 dBm to -59 dBm in 1 dB steps. The Spectrum Analyzer/Tracking Generator system can be used to display frequency response of various devices such as filters, amplifiers, etc. that are connected between the tracking generator RF OUTput and the spectrum analyzer rf input connector. When the TR 502 is installed in a modified three-wide or larger, power module, a frequency counter such as the DC 502 can be connected to the AUX OUT and used to accurately measure the frequency for any fixed position of span. When the analyzer is in the non-sweep mode, the TR 502 output is a cw signal and the counter reads continuously. If a DC 502 Option 7, or similar counter is used, the TRACKING GEN LOGIC is interfaced with the 7L13 Spectrum Analyzer so operational logic from the TR 502 controls the sweep function of the spectrum analyzer and the frequency counting of the counter A dot is displayed at sweep center to indicate where and when the frequency count is taken.