CMC251 1.3 GHz Frequency Counter:The 10 MHz internal time base (using a highly stabilized crystal oscillator) provides a single-shot resolution of 100 ns. Measurement results are displayed using an eight digit display, automatically placing the decimal appropriately. The CMC251 Frequency Counter has a locking, multiposition handle that folds under the instrument. The instrument is delivered with a 115 V power cord, an installed fuse for 115 V operation, and this manual.