connector 50 through a 52 u03c9 resistor 54 to ground in a second or transmit test position the contact arms of switches s1 1 and s1 4 are on open terminals and the contact arm of switch s1 2 connects terminals a and a 39 while the contact arm of switch s1 3 connects the inner lead of connector 50 via a coaxial lead 56 with a frequency counter circuit 57 supplying a frequency signal to digital frequency meter 27 and a power and modulation transmit test circuit 58 which is grounded through a 52 u03c9 resistor 60 the lead 56 being controlled by a relay r1 operated by b 39 voltage from the power supply via terminals a a 39 and switch s1 2 in a third or receive test position the contact arms of switches s1 1 and s1 2 are on open terminals and the switch arms of switches s1 3 and s1 4 are connected to common terminals such that the inner lead of connector 50 is connected with the output of an rf output level control circuit 62 of a 23 channel receive test circuit 63 the output level control circuit 62 receiving an input from a 23 channel rf synthesizer 64 which receives inputs from a channel selector 66 to control channel frequency from a 1000 hz oscillator 68 to produce a modulated test signal the output of rf level control 62 is also connected with signal level meter 24 the frequency counter circuit 57 can be of any conventional circuitry and for example the.