TM 1-1510-224-10 NOTE The   ACT   annunciator   continuing   to flash   after   the   frequency   has   been selected indicates that the transceiver     is     not     tuned     to     the frequency    displayed    in    the    active display. To    return    to    the    preset    frequency    selection mode,  push  the  ACT  switch  again  for  about  2  seconds. As a safety feature, the transceiver control unit switches to     the     active     frequency     selection     mode     when     a frequency select knob is operated while the STO, TEST, or XFR/MEM switches are actuated. (4) Frequency   storage.      To   program the     memory,     select     the     frequency     in     the     preset frequency  display  using  the  frequency  select  knobs  and push the STO switch once.  One of the channel numbers (CH 1 through CH 6)  will  appear  in  the  active  display  for approximately  5  seconds.    During  this  time  the  channel number   can   be   changed   without   changing   the   preset frequency   by   momentarily   positioning   the    XFR/MEM switch to the   MEM  position.    After  the  desired  channel number has been selected, push the   STO  switch  again to store the frequency. NOTE When storing a frequency, the second  actuation  of  the  STO  switch must  be  done  within  5  seconds  after selecting  the  channel  number  or  the first  actuation  of  the  STO  switch.    If more    than    5    seconds    elapse,    the control    will    revert    to    the    normal modes  of  operation  and  the  second store command will be interpreted as the first store command. After a frequency has been stored in memory, it will remain there until changed by using the STO switch. Memory  is  retained  even  when  the  unit  is  turned  off  for an extended period of time. (5) Stuck   microphone   switch.      Each time the push-to-talk switch is depressed, the microprocessor    in    the    transceiver    starts    a    2-minute timer.  (The   TX  annunciator  on  the  transceiver  control unit   will   be   illuminated   when-ever   the   transmitter   is transmitting.)  If  the  transmitter  is  still  transmitting  at  the end  of  2  minutes,  the  microprocessor  turns  it  off.    Most intentional transmissions last much less than 1 minute; a 2-minute transmission is most likely the result of a stuck microphone switch.  This timing feature protects the ATC channel from long-term interference. When it turns off the transmitter, the microprocessor    switches    the    transceiver    to    receive operation.    A  stuck  microphone  switch  will  prevent  you from hearing received Table 3-1.  VHF Communications Transceiver Fault Codes CODE INTERPRETATION 00 No fault found 01 5 V dc below limit 02 5 V dc above limit 03 12 V do below limit 04 1 2 V dc above limit 05 Synthesizer not locked 07 - Noise squelch open without signal 08 Noise squelch not open with signal 12 BCD frequency code invalid 13 2-out-of-5 frequency code invalid 14 Serial message invalid 15 Frequency out of range 16 Forward power below limit 17 Transmitter temperature excessive 21 Tuning voltage out of limit at highest receive frequency 22 Tuning voltage out of limit at 118 MHz 23 Local oscillator output below limit 24 No-signal AGC voltage too high 25 Inadequate AGC voltage increase with RF signal 26 Reflected RF power above limit 27 Transmitter timed out BT03838 3-10