Ideal for portable measurement applications, the model TF960 battery-powered counter-timer from Saelig Co. can measure and count signal frequency between 0.001 Hz and 6000 MHz with high sensitivity and accuracy, using a reciprocal counting technique. It incorporates an internal temperature-compensated-crystal-oscillator (TCXO) frequency reference to achieve measurement stability of ±1 ppm across its operating temperature range. It can measure frequency, period, pulse width, duty cycle, and frequency ratio, as well as event counting/totalizing. For frequencies to 125 MHz, the input can be configured as 1MΩ or 50-Ω impedance; with AC or DC coupling; and the active edge can be a positive or negative transition. The instrument also includes two high-frequency input ports for ranges of 80 MHz to 3 GHz and 2 to 6 GHz, the latter with a Type-N connector. The counter-timer operates for typically 24 h from internal rechargeable nickel-metal-hydride (NiMH) batteries; it can also be powered via its standard Universal Serial Bus (USB) port, or continuously with its AC adapter/charger. It measures just 10.3 x 3.5 x 9.3in. and weighs less than 2 lbs, showing results on a high-contrast display with 10-digital resolution.