4.—(1) The exemption provided for in regulation 3 shall be limited to equipment which —
(a)operates in the frequency band between 865 MHz and 868 MHz;
(b)operates using one or more of the frequency channels which have a centre frequency specified in the Schedule and which have a bandwidth no greater than 200 kHz;
(c)does not cause or contribute to any undue interference to any wireless telegraphy; and
(d)emits transmissions which —
(i)at frequencies between 865 MHz and 865.6 MHz have an erp no greater than 100 mW;
(ii)at frequencies between 865.6 MHz and 867.6 MHz have an erp no greater than 2 Watts; and
(iii)at frequencies between 867.6 MHz and 868 MHz have an erp no greater than 500 mW.
(2) Where equipment is an interrogator, the exemption provided for in regulation 3 shall, additionally, be limited to equipment which —
(a)transmits with a beam-width which —
(i)at an erp less than or equal to 500 mW is less than or equal to ninety degrees; and
(ii)at an erp greater than 500 mW is less than or equal to seventy degrees;
(b)only begins transmitting in any channel—
(i)at an erp greater than 500mW, if the signal level at the receiver of the interrogator from other equipment operating within that channel is less than or equal to –96 dBm for a period of not less than five milliseconds immediately prior to transmission;
(ii)at an erp greater than 100mW, but less than or equal to 500mW, if the signal level at the receiver of the interrogator from other equipment operating within that channel is less than or equal to –90 dBm for a period of not less than five milliseconds immediately prior to transmission; and
(iii)at an erp less than or equal to 100mW, if the signal level at the receiver of the interrogator from other equipment operating within that channel is less than or equal to –83 dBm for a period of not less than five milliseconds immediately prior to transmission;
(c)operates so that the duration of each transmission is no longer than four seconds; and
(d)operates with an interval between each transmission on the same frequency channel of not less than 100 milliseconds.