Sec. 22.915  Modulation requirements.

    Cellular systems must be capable of providing service using the 
types of modulation described in the cellular system compatibility 
specification.
    (a) Non-voice modulating signals. Modulating signals other than 
voice signals, such as data signals, may be transmitted, provided the 
resulting modulated emission exhibits spectral characteristics not 
exceeding those resulting from voice modulation.
    (b) Modulation levels. The levels of the modulating signals must be 
set to the values specified in this paragraph, and must be maintained 
within &177;10% of those values.
    (1) The instantaneous frequency deviation resulting from the main 
modulating signal must be &177;12 kHz.
    (2) The instantaneous frequency deviation resulting from the 
supervisory audio tones must be &177;2 kHz.
    (3) The instantaneous frequency deviation resulting from the 
signaling tone must be &177;8 kHz.
    (4) The instantaneous frequency deviation resulting from wideband 
data signals must be &177;8 kHz.
    (c) Deviation limitation circuitry. Cellular transmitters must be 
equipped with circuitry that automatically prevents modulation levels 
for voice transmissions from exceeding the limits specified in this 
section.
    (d) Audio filter characteristics. Except as provided in Sec. 22.917, 
radiotelephony signals applied to the modulator from the modulation 
limiter must be attenuated as a function of frequency as specified in 
this paragraph.
    (1) For mobile stations, these signals must be attenuated, relative 
to the level at 1 kHz, as follows:
    (i) In the frequency ranges of 3.0 to 5.9 kHz and 6.1 to 15.0 kHz, 
signals must be attenuated by at least 40 log (f3) dB, where f 
is the frequency of the signal in kHz.
    (ii) In the frequency range of 5.9 to 6.1 kHz, signals must be 
attenuated at least 35 dB.
    (iii) In the frequency range above 15 kHz, signals must be 
attenuated at least 28 dB.
    (2) For base stations, these signals shall be attenuated, relative 
to the level at 1 kHz, as follows:
    (i) In the frequency range of 3 to 15 kHz, signals must be 
attenuated by at least 40 log (f3) dB, where f is the frequency 
of the signal in kHz.

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    (ii) In the frequency range above 15 kHz, signals must be attenuated 
by at least 28 dB.
    (3) Filtering is not required for the supervisory audio tones, 
signaling tones or wideband data signals.