AN4147

An overview of FCC regulations

Doc ID 023516 Rev 1

3/14

1

An overview of FCC regulations

1.1

Part 15.231

Devices operating in the 315 MHz band must comply with section 15.231 of the FCC Title 47

Part 15 [

2] regulations. The provisions in section 15.231 are restricted to periodic operation

within the 40.66 - 40.70 MHz band and above 70 MHz. The intentional radiator is restricted

to the transmission of a control signal such as those used with alarm systems, door

openers, remote switches, etc. Continuous transmissions, voice, video and radio control of

toys are not permitted. Data is permitted to be sent with a control signal.

To comply with the provisions for periodic operation, the following conditions must be meet:

●

A manually operated transmitter shall employ a switch that will automatically deactivate

the transmitter within not more than 5 seconds of being released. A transmitter

activated automatically shall cease transmission within 5 seconds after activation.

●

Periodic transmissions at regular predetermined intervals are not permitted. However,

polling or supervision transmissions, including data, to determine system integrity of

transmitters used in security or safety applications are allowed if the total duration of

transmissions does not exceed 2 seconds per hour.

●

Intentional radiators which are employed for radio control purposes during

emergencies involving fire, security and safety of life, when activated to signal an

alarm, may operate during the pendency of the alarm condition.

●

In addition to the provisions of 15.205, the field strength of emissions from intentional

radiators operated under this section shall not exceed the values in

Table 1. The field

strength limits are specified at a distance of 3 meters.

●

The limits on the field strength of the spurious emissions in the

Table 1 are based on

the fundamental frequency of the intentional radiator. Spurious emissions shall be

attenuated to the average limits shown in this table or to the general limits shown in

section 15.209, whichever limit permits higher field strength.

●

The bandwidth of the emission shall be no wider than 0.25% of the center frequency.

Bandwidth is determined at the points 20 dB down from the modulated carrier.

●

Intentional radiators may operate at a periodic rate exceeding that specified in point 1

and may be employed for any type of operation, including operation prohibited in point

1. In this case, the max field strength is different and is shown in the

Table 2. The

device operating in the condition described in this point shall be provided with a means

for automatically limiting operation so that the duration of each transmission shall not

be greater than 1 second and the silent period between transmissions shall be at least

30 times the duration of the transmission, but in no case less than 10 seconds.

Table 1.

Field strength of emissions for normal working conditions

Fundamental frequency

[MHz]

Field strength of fundamental

[µV/m]

Field strength of spurious emission

[µV/m]

40.66 – 40.70

2250

225

70 – 130

1250

125

130 – 174

1250 to 3750

125 to 375

174 – 260

3750

375