  For the EL CVn candidate 1SWASPJ181417.43+481117.0 (WASP 1814+48), we secured
the first spectroscopic observations between 2015 April and 2021 March. Using
the echelle spectra, the radial velocities (RVs) of the primary star were
measured with its atmospheric parameters of $T_{\rm eff,1}=7770\pm130$ K and
$v_1$$\sin$$i=47\pm6$ km s$^{-1}$. We fitted our single-lined RVs and the TESS
light curve simultaneously. From the binary modeling, we determined the
following fundamental parameters for each component: $M_1=1.659\pm0.048$
$M_\odot$, $R_1=1.945\pm0.027$ $R_\odot$, and $L_1=12.35\pm0.90$ $L_\odot$ for
WASP 1814+48 A, and $M_2=0.172\pm0.005$ $M_\odot$, $R_2=0.194\pm0.005$
$R_\odot$, and $L_2=0.69\pm0.07$ $L_\odot$ for WASP 1814+48 B. The surface
gravity of $\log g_2=5.098\pm0.026$ obtained from $M_2$ and $R_2$ is concurrent
with 5.097$\pm$0.025 computed directly from the observable quantities. WASP
1814+48 B is well-matched with the 0.176 M$_\odot$ white dwarf (WD)
evolutionary model for $Z=0.01$. The metallicity and our Galactic kinematics
indicate that the program target is a thin-disk star. The whole light residuals
after removal of the binary trend were analyzed and found to oscillate at a
total of 52 frequencies. Among these, most of the low frequencies below 24
day$^{-1}$ are aliases and orbital harmonics. The five significant frequencies
between 32 and 36 day$^{-1}$ are the pulsation modes of WASP 1814+48 A located
in the $\delta$ Sct domain on ZAMS, and the high frequencies of 128$-$288
day$^{-1}$ arise from WASP 1814+48 B in the pre-He WD instability strip. Our
results reveal that WASP 1814+48 is the fifth EL CVn star that is composed of a
$\delta$ Sct-type primary and a pre-ELMV (extremely low-mass pre-He WD
variable).
