placeholder for additional info later
Early systems used these frequencies for the base units: 1.665, 1.690, 1.695, 1.710, 1.725, 1.730, 1.750, 1.755, 1.770 MHz.
And for the handsets: 46.610, 46.630, 46.670, 46.710, 46.730, 46.770, 46.830, 46.870, 46.930, 46.970, 49.670, 49.770, 49.830, 49.845, 49.860, 49.875, 49.890, 49.930, 49.970, 49.990 MHz
Both base and handset (portable unit) used frequency modulation. The 1665 kHz, 1690 kHz and 1710 kHz frequencies eventually became part of the expanded AM broadcast band.
The second-generation of analog cordless phones were 10-channel FM units operating in the 46.61 MHz to 46.97 MHz (base stations) and 49.67 MHz to 49.99 MHz under Part 15 47 CFR 15.233 using the following frequency pairs.
- Base Frequency 46.610 MHz - Handset Frequency 49.670 MHz
- Base Frequency 46.630 MHz - Handset Frequency 49.845 MHz
- Base Frequency 46.670 MHz - Handset Frequency 49.860 MHz
- Base Frequency 46.710 MHz - Handset Frequency 49.770 MHz
- Base Frequency 46.730 MHz - Handset Frequency 49.875 MHz
- Base Frequency 46.770 MHz - Handset Frequency 49.830 MHz
- Base Frequency 46.830 MHz - Handset Frequency 49.890 MHz
- Base Frequency 46.870 MHz - Handset Frequency 49.930 MHz
- Base Frequency 46.930 MHz - Handset Frequency 49.990 MHz
- Base Frequency 46.970 MHz - Handset Frequency 49.970 MHz
The "49 MHz" cordless phones were rapidly adopted by consumers, resulting in heavy frequency congestion. The 49.830-49.890 MHz frequencies were and still are heavily used by other devices including baby monitors in continuous transmit mode. 15 frequencies were added bringing the total number of channels to 25. 43.71 MHz to 44.49 MHz (43.72 MHz to 44.48 MHz), 46.60 MHz to 46.98 MHz (46.61 MHz to 46.97 MHz), 48.75 MHz to 49.51 MHz (48.76 MHz to 49.50 MHz and 49.66 MHz to 50.0 MHz (49.67 MHz to 49.9 MHz). Note that the frequencies overlap with the VHF low band business radio band, the military bands, the 49 MHz RC 49 MHz remote control device frequencies and 49 MHz short range devices (walkie-talkies, baby monitors, etc.) The original 10 channel cordless phones used the 46.6 MHz - 47.0 MHz and 49.6 MHz to 50.0 MHz ranges only (46.610 MHz - 46.970 MHz and 46.670 MHz - 49.990 MHz).
The handset/headset transmit frequencies for channels 17, 18, 20, 21 and 22 overlap with the 49.82-49.90 MHz frequencies, including frequencies used by baby monitors. When these cordless phones were popular, issues with interference due to baby monitors was common (and hearing your neighbor's phone call over your baby monitor was also common).
15.233 Operation within the bands 43.71-44.49 MHz, 46.60-46.98 MHz, 48.75-49.51 MHz and 49.66-50.0 MHz. (a) The provisions shown in this section are restricted to cordless telephones.
(b) An intentional radiator used as part of a cordless telephone system shall operate centered on one or more of the following frequency pairs, subject to the following conditions:
(1) Frequencies shall be paired as shown below, except that channel pairing for channels one through fifteen may be accomplished by pairing any of the fifteen base transmitter frequencies with any of the fifteen handset transmitter frequencies.
- Base Frequency 43.720 MHz - Handset Frequency 48.760 MHz - Channel 1
- Base Frequency 43.740 MHz - Handset Frequency 48.840 MHz - Channel 2
- Base Frequency 43.820 MHz - Handset Frequency 48.860 MHz - Channel 3
- Base Frequency 43.840 MHz - Handset Frequency 48.920 MHz - Channel 4
- Base Frequency 43.920 MHz - Handset Frequency 49.020 MHz - Channel 5
- Base Frequency 43.960 MHz - Handset Frequency 49.080 MHz - Channel 6
- Base Frequency 44.120 MHz - Handset Frequency 49.100 MHz - Channel 7
- Base Frequency 44.160 MHz - Handset Frequency 49.160 MHz - Channel 8
- Base Frequency 44.180 MHz - Handset Frequency 49.200 MHz - Channel 9
- Base Frequency 44.200 MHz - Handset Frequency 49.240 MHz - Channel 10
- Base Frequency 44.320 MHz - Handset Frequency 49.280 MHz - Channel 11
- Base Frequency 44.460 MHz - Handset Frequency 49.360 MHz - Channel 12
- Base Frequency 44.400 MHz - Handset Frequency 49.400 MHz - Channel 13
- Base Frequency 44.460 MHz - Handset Frequency 49.460 MHz - Channel 14
- Base Frequency 44.480 MHz - Handset Frequency 49.500 MHz - Channel 15
- Base Frequency 46.610 MHz - Handset Frequency 49.670 MHz - Channel 16
- Base Frequency 46.630 MHz - Handset Frequency 49.845 MHz - Channel 17
- Base Frequency 46.670 MHz - Handset Frequency 49.860 MHz - Channel 18
- Base Frequency 46.710 MHz - Handset Frequency 49.770 MHz - Channel 19
- Base Frequency 46.730 MHz - Handset Frequency 49.875 MHz - Channel 20
- Base Frequency 46.770 MHz - Handset Frequency 49.830 MHz - Channel 21
- Base Frequency 46.830 MHz - Handset Frequency 49.890 MHz - Channel 22
- Base Frequency 46.870 MHz - Handset Frequency 49.930 MHz - Channel 23
- Base Frequency 46.930 MHz - Handset Frequency 49.990 MHz - Channel 24
- Base Frequency 46.970 MHz - Handset Frequency 49.970 MHz - Channel 25
The FCC quickly moved to authorize additional frequency space for cordless phones. With the 900 MHz ISM band 902-928 MHz becoming available next. 900 MHz cordless phones are still used today. Analog FM, digital voice and various frequency hopping spread-spectrum or FHSS cordless phones became available for the 900MHz band. If FHSS technology is used, base stations may transmit up to 1 watt ERP. This increase in transmitter power combined with the interference rejection capabilities of spread spectrum gave the higher-end 900 MHz cordless phones significant range. Unlike the older-generation models, 900 MHz cordless telephones never had a standardized channel plan or base and handset frequency pair or channel plan. This meant that manufacturers simply created their own, with widely differing channel steps, number of channels and other options. Even cheap analog FM 900 MHz cordless phones usually featured automatic channel selection. In other words, if the first channel pair was busy the system simply switched to the next clear channel. This same technology was (and is) included in digital voice cordless telephones operating in the 900 MHz band, the 2.4 GHz band and the 5.8 GHz band as well as those using modern DECT technology.
The 2.4 GHz band became available shortly after 900 MHz and originally provided excellent results. However, the proliferation of devices operating in the 2.4 GHz band now means that 2.4GHz cordless phones often suffer from (or cause) interference and/or have reduced range compared to the other bands. The 5.8 GHz allocation was opened up to alleviate the congestion on 2.4 GHz. Many 5.8 GHz band cordless phones are sold today. Some "5.8 GHz" phones are actually cross-band and use 5.8 GHz for handset to base but use 900 MHz or 2.4 GHz for base-to-handset.
DECT (branded as "DECT 6.0" in the United States and Canada) actually operates in the 1.8 GHz and 1.9 GHz band but provides interference free cordless phone service and is extremely adaptable for business, retail, industrial, office or home use. DECT phone systems may be expanded with numerous base stations, full-duplex intercoms and other systems in a cellular-like network. This includes PBX telephone systems in offices, retail stores, etc. DECT is effectively the convergence of cellular technologies and single-base/single-handset cordless phones.
CT0 - UK Specification - original cordless phone standard. 10mW power output, FM mode.
47.4 MHz to 47.550 MHz (47.45 MHz to 47.55 MHz)
- Base Frequency: 1642 kHz 1.642 MHz - Handset Frequency: 47.45625 MHz - Channel 1
- Base Frequency: 1662 kHz 1.662 MHz - Handset Frequency: 47.46875 MHz - Channel 2
- Base Frequency: 1682 kHz 1.682 MHz - Handset Frequency: 47.48125 MHz - Channel 3
- Base Frequency: 1702 kHz 1.702 MHz - Handset Frequency: 47.49375 MHz - Channel 4
- Base Frequency: 1722 kHz 1.722 MHz - Handset Frequency: 47.50625 MHz - Channel 5
- Base Frequency: 1742 kHz 1.742 MHz - Handset Frequency: 47.51875 MHz - Channel 6
- Base Frequency: 1762 kHz 1.762 MHz - Handset Frequency: 47.53125 MHz or 47.44375 MHz - Channel 7
- Base Frequency: 1782 kHz 1.782 MHz - Handset Frequency: 47.54375 MHz - Channel 8
CT0 - UK Specification CT0 Extended - Long Range 100mW power output
- Base Frequency: 47.43125 MHz - Handset Frequency: 77.5125 MHz
- Base Frequency: 47.41875 MHz - Handset Frequency: 77.5000 MHz
CT0 - UK Specification CT0 - Current Allocation - 10mW power output, FM mode. 31.025 MHz - 31.225 MHz and 39.925 MHz - 40.125 MHz.
- Base Frequency: 31.0375 MHz - Handset Frequency: 39.9375 MHz - Channel 1
- Base Frequency: 31.0625 MHz - Handset Frequency: 39.9625 MHz - Channel 2
- Base Frequency: 31.0875 MHz - Handset Frequency: 39.9875 MHz - Channel 3
- Base Frequency: 31.1125 MHz - Handset Frequency: 40.0125 MHz - Channel 4
- Base Frequency: 31.1375 MHz - Handset Frequency: 40.0375 MHz - Channel 5
- Base Frequency: 31.1625 MHz - Handset Frequency: 40.0625 MHz - Channel 6
- Base Frequency: 31.1875 MHz - Handset Frequency: 40.0875 MHz - Channel 7
- Base Frequency: 31.2125 MHz - Handset Frequency: 40.1125 MHz - Channel 8
CT2 - 100 kHz channel spacing 864.1 MHz to 868.1 MHz.
Cordless telephony Equipment operating in the Frequency Range 864.1- 868.1 MHz (CT2) 2-level frequency shift keying. 10mW transmit power limit. 40 channels at 100 kHz channel spacing. Base frequencies 864.1 MHz to 868.1 MHz. Handset frequencies 864.1 MHz - 868.1 MHz. The UK is assigning other services to the 864-868 MHz band but CT2 equipment remains legal to use.
DECT 1880-1900 MHz - <250mW handset and base stations 1880-1900 MHz on the standard GMSK modulation type using TDMA. CEPT DECT standard.
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