TM 55-1510-219-10 NB Limits  selectivity  to  narrow- band intermediate frequency. WB Limits selectivity to wide-band intermediate frequency of FM band. MEM  LOAD Momentary  switch.  If pressed, loads manually selected frequen- cy in preset channel memory AM  SQUELCH Screwdriver adjustable potenti- control ometer.  Squelch fully overridden at full counter-clockwise posi- tion.  Clockwise rotation in- creases input signal required to open squelch. Mode select Three-position rotary switch. switch OFF Shuts off receiver-transmitter. TR Selects transmit/receive modes. DF Not used. SQ/DIS/TONE Three-position switch. select switch Center Selects squelch function, SQ/DIS Shuts off squelch function. TONE Transmits tone of approx.  1000 Hz. Frequency Four-position switch. control emergency/select switch PRE Enables preset channel selection. MAN Enables manual frequency selec- tion. EMER AM or Selects a prestored guard chan- FM nel. VOL control Clockwise rotation increases volume. c.  Normal Operation. (1)  Turn-on. 1.  Mode select switch (VHF AM/FM panel) - TR. (2)  Receive. 1.      Frequency   control   emergency   select switch   (fig.      3-5)   -   MAN   or   PRE,   as desired. 2.      Transmitter-interphone   selector   (audio panel, fig.  3-1) - #2 position.  or Audio monitor control #2 - ON. 3. Manual frequency/preset channel selectors - Set desired frequency. 4.  VOL control - As required. (3)  Transmit. 1.  Transmit/interphone select switch (audio panel) -Position 2. 2.  Microphone switch - Press. (4)  Shutdown. 1.  Mode select switch (fig.  3-5) - OFF. d.  VHF AM/FM - Emergency Operation. (1)  Emergency AM Mode. 1.  Transmit/interphone select switch (audio panel) -Position 2. 2.  Mode select switch - TR. 3.        PRE-MAN-FM/AM        EMER    switch    - EMER AM. 4. Manual frequency/preset channel selector - Set emergency frequency. 5.  Microphone switch - Press. (2)  Emergency FM Mode. 1.        Transmit-interphone    selector    (audio panel, fig.  3-1) - #2 position. 2.      Mode   select   switch   -   TR   or   DF,   as desired. 3.        PRE-MAN-FM/AM        EMER    switch    - EMER FM. 4. Manual frequency/preset channel selector - Set emergency frequency. 5.  Microphone switch - Press. 6.  Shutdown Mode select switch - OFF. 3-11