Plugs into the accessory socket of the Model 540. Six digits show actual transmitted and received frequencies to hundreds of Hertz. The VFO output frequency, which is 9 MHz away from the operating frequency, is counted and a 9 MHz preset is either added to or subtracted from the count by means of the front panel mode switch, thus eliminating all VFO crystal tolerance errors. The 9 MHz oscillator tolerance error is eliminated by setting the time base gating oscillator to WWV. A COUNT position on the mode switch permits using the 244 as a straight 50 kHz to 22 MHz frequency counter. Includes cable. Housed in matching enclosure.