The 575B and 578B CW frequency counters are distinguished by their fully automatic source-locking capability. Virtually any electronically tunable frequency source can be locked to the same accuracy and long-term stability as the time base oscillators inside the 575B and 578B. The ability of these counters to accurately set and stabilize the frequency of a basic frequency source can many times save the expense of a synthesized signal generator. The locked frequency is settable in 10 kHz increments from 10 MHz to the maximum frequency of the counter. The 20 GHz 575B and the 26.5 GHz 578B (110 GHz optional) are fully programmable via GPIB thereby making the locked source an easily integrated par of an ATE system.

All Phase Matrix EIP® brand frequency counters are based on a unique heterodyne architecture that incorporates a YIG-based preselector. The YIG-preselected input provides unparalleled performance, in amplitude discrimination, frequency selectivity, kickback noise, and burnout protection.