Hi Howard, The K4 will have built-in transmit monitoring. Wayne N6KR > On Oct 2, 2020, at 8:21 PM, Howard Saxion via Elecraft <elecraft at mailman.qth.net> wrote: > > Will the transmit monitor currently used with a P3 work with the K4? If not, will the K4 have similar functionality provided by the P3 and transmit monitor? > Howard/WX7HS