A more general form of the digitizer transfer function (equation 22) is:
Similarly the frequency response of a geophone can be expressed as:
where q and Q are polynomials in s.
The combined
frequency response of a digitizer and a seismometer is the multiple of
the two response functions, 
for the digitizer
and 
for the response of the geophone, i.e.:
where 
and 
are the gains of the digitizer and
geophone and p, P, q and Q are polynomials.
For the RD3/OSD3,
p(s) is of first order and P(s) of forth order. For the Lennartz
geophones, both q(s) and Q(s) are second order polynomials, where as
for the Streckheisen STS-2 q(s) is of order three and Q(s) of order
eleven.
The velocity proportional frequency response of the SIL system is shown in Figure 4 for the six types of geophones.
The total gain of the system is the multiple of
the filter gain 
(equation 14),
the frequency independent
gain 
of the digitizer (equation 17),
and
the generation constant of the geophone, , i.e.:
For the Lennartz geophones is 400.0 V/m/s while for Guralp
seismometers from the Passcal instrument pool is 2000.0 V/m/s,
giving a factor five difference in over all gain.
