Transcribed from printed pages by the Field Services Department of the 
American Radio Relay League, Inc., 225 Main St., Newington, CT 06111, 
(203) 666-1541.

                  TELEPHONE INTERFERENCE SURVEY

                        February 28, 1994

                  Telephone Interference Survey

Background

The Federal Communications Commission (FCC) receives 25,000 
complaints per year from individuals who are unable to use their 
telephones because nearby radio stations interfere with the proper 
operation of the telephones.  Whenever the radio stations are on 
the air, the telephones pick up their transmissions which then 
override any ongoing telephone conversation.

The FCC's Field Operations Bureau (FOB) has done an informal 
survey to obtain information about telephone interference such as:

     - which telephones are affected
     - what type transmitting stations are involved
     - the power levels at which the stations were transmitting
     - whether commonly available filters would be effective in 
       eliminating the interference
     - whether specially designed telephones would be effective in 
       eliminating the interference

In setting forth the results of its informal survey, FOB 
emphasizes that, because this survey is based on a random sample 
it cannot be claimed that identical results would be derived under 
scientific surveying and testing, nor should the results be 
construed as FCC endorsement or criticism of any particular 
manufacturer's product.  Rather, FOB believes these results to be 
a good "first look" at the problem.

Procedure

Thirty-five FCC field offices across the country participated in 
the survey.  Each office was to choose three recent complaints of 
telephone interference on a random basis, and then to investigate 
the complaints.

At the transmitting station FOB staff would determine the type of 
station (i.e., amateur, citizens band, broadcast, etc.), measure 
the station power, and obtain information on antenna height, 
antenna gain, and distance from the complainant.

At the complainant's location, FOB would disconnect all 
telephones, take them to a chosen telephone jack, and plug them in 
one at a time while the station was transmitting.  FOB would then 
record which telephones received interference and which did not.

FOB also tested the effectiveness of several commercially-
available telephone filters, connecting the filters to telephones 
which were receiving interference while the radio station was 
transmitting.

Finally, FOB connected "bulletproof" telephones to the telephone 
jacks and observed whether these telephones received interference.  
A "bulletproof" telephone is one that is specially designed to be 
immune to interference.

Findings

                      Types of Transmitting Stations

FOB inspected 108 transmitting stations which were involved in the 
telephone interference complaints, as follows:

                     Citizens Band             47
                     Amateur                   27
                     AM Broadcast              23
                     FM Broadcast              10
                     International Broadcast    1

                               Power Levels

The power levels of the radio transmitting stations varied from 
two watts to half a million watts.  One-third of the transmitting 
stations operated with less than ten watts, and one-third of the 
interfering stations were broadcast stations using between 3000 
and half a million watts.  Attachment 1 lists the power levels of 
the transmitting stations.

                            Types of Telephones

FOB tested 241 telephones found in the complainants' residences 
for interference.  Of the 241 telephones 68 percent received 
interference.  Attachment 2 lists the telephones tested.  FOB did 
not observe interference on 32 percent of the telephones it 
tested.  These telephones are listed in Attachment 3.

                             Types of Filters

FOB tested the effectiveness of the AT&T Z100B1 filter on 138 
telephones receiving interference.  After connecting the filter to 
the telephones, 62 percent of the telephones continued to receive 
interference.  The filter did eliminate interference on 38 percent 
of the telephones.  A number of other filters were also tested on 
82 telephones receiving interference.  As a group these filters 
eliminated interference on 29 percent of the telephones.  They did 
not eliminate interference on 71 percent of the telephones.  
Attachment 4 lists the filters which eliminated the interference.

                          Bulletproof Telephones

The FCC tested "bulletproof" telephones at 52 locations where the 
individuals were receiving interference to their telephones.  The 
"bulletproof" telephones eliminated interference at 96 percent of 
the locations.
                                                      
Conclusions

The transmitting stations most likely to cause telephone 
interference are citizens band, amateur, and broadcast stations.  
Citizens band stations accounted for half the telephone 
interference cases.  Amateur stations and broadcast stations 
accounted for the other half.

The power levels used by the radio transmitting station did not 
appear to be a significant factor in causing telephone 
interference.  Power levels of 10 watts or less caused telephone 
interference in a third of the cases.

A large portion of the residential telephones appeared to be 
susceptible to interference from nearby radio transmitting 
stations.  Although some telephones did not receive interference, 
the limited nature of the testing performed in conjunction with 
this survey would not support the conclusion that they would 
always reject interference.

Telephone interference filters cannot be relied upon to eliminate 
telephone interference: in two out of three cases in the test 
sample, they did not work.  Manufacturers can design telephones to 
be interference free.  "Bulletproof" telephones were immune from 
interference virtually all of the time.

A Final Note

Notwithstanding the 25,000 reports of telephone interference the 
FCC has received to date, it is FOB's experience that, as large as 
this number is, it probably represents only a fraction of the 
actual instances in which this interference occurs.  Given the 
enormous numbers of instances in which this type of interference 
is experienced by consumers, it is our hope that this survey, 
notwithstanding its informality, will serve as a catalyst for 
affected parties to productively address and resolve this problem.  
As always, FOB remains ready to assist in that effort.

                               ATTACHMENT 1

                          FIELD OPERATIONS BUREAU                            
                       TELEPHONE INTERFERENCE SURVEY
                   POWER LEVELS OF INTERFERENCE SOURCES

                             UNKNOWN      2 sources
                             2 watts      4 sources
                             3 watts      7 sources
                             4 watts     14 sources
                             5 watts      7 sources
                             6 watts      1 source
                             7 watts      4 sources
                            12 watts      2 sources
                            26 watts      1 source
                            30 watts      1 source
                            35 watts      1 source
                            50 watts      1 source
                            53 watts      1 source
                            54 watts      1 source
                            57 watts      1 source
                            75 watts      1 source
                            80 watts      1 source
                           100 watts      5 sources
                           101 watts      1 source
                           110 watts      2 sources
                           114 watts      1 source
                           131 watts      1 source
                           150 watts      1 source
                           160 watts      1 source
                           200 watts      1 source
                           250 watts      1 source
                           438 watts      1 source
                           462 watts      1 source
                           500 watts      3 sources
                           600 watts      1 source
                           800 watts      1 source
                         1,000 watts      3 sources
                         1,500 watts      2 sources
                         3,000 watts      2 sources
                         5,000 watts      5 sources
                         8,000 watts      1 source
                        10,000 watts      4 sources
                        16,000 watts      1 source
                        25,000 watts      1 source
                        50,000 watts     11 sources
                        51,000 watts      4 sources
                        54,000 watts      1 source
                       100,000 watts      1 source
                       500,000 watts      1 source
                       
                       Total sources:   108

                               ATTACHMENT 2

                          FIELD OPERATIONS BUREAU
                       TELEPHONE INTERFERENCE SURVEY
                     TELEPHONES RECEIVING INTERFERENCE

fo fil ix   power att oth fcc make              model

DL  N  AMA    800  N   N   Y  (UNKNOWN)         (UNKNOWN) 
AL  N  CB       4  N   N   Y  (UNKNOWN)         (UNKNOWN) 
PL  N  CB       2  N   N   Y  AT&T              (NONE) 
DT  N  CB       5  N   N   Y  AT&T              (NONE) (FCC AS593M-70230) 
LR  N  AM    1000  Y          AT&T              100 
KI  N  FM    3000  N          AT&T              1306 
KI  N  AMA    100  N          AT&T              1504 
DV  N  AM    5000  Y   Y   Y  AT&T              150E 
NY  N  CB       3  Y   Y      AT&T              1510 
PO  N  AMA     35  Y   N      AT&T              1521 
BS  N  AM   10000  Y   N      AT&T              1532 
GI  N  AMA     53  N   N      AT&T              1611 
DL  Y  CB       5  N       Y  AT&T              1618 
KI  N  AMA    100  N          AT&T              210 
KI  N  AMA    100  N          AT&T              210 
DS  N  AM    5000          Y  AT&T              210 
DS  Y  AMA    500  N   Y      AT&T              210 
NF  Y  CB       3  Y   N   Y  AT&T              210 
PL  N  AMA   1000  Y   Y   Y  AT&T              530 
DL  N  AMA    800  Y   Y   Y  AT&T              5455 
GI  N  AMA    101  N          AT&T              610 
BF  N  AMA    100  N       Y  AT&T              710 
KI  N  CB       5  N          AT&T              720 
CG  N  AMA   1000  Y       Y  AT&T              720 
KC  Y  CB       4  N       Y  AT&T              725 
GI  N  AMA    101  N          AT&T              725 
PA  N  CB       3  N       Y  AT&T              732 
HL  N  AMA    462  N   N      AT&T              732 
MA  Y  AMA    600  N          AT&T              AOM9RN 10451-TE-E 
LR  Y  CB       4  N          AT&T              AS 550Z 71597 
MA  N  AMA     50  N          AT&T              ASSS0Z-71597-TE-E 
DT  N  AM     438      N      AT&T              MODEL 1506 
NY  N  AM   25000  N   N      AT&T              PRINCESS 
BM  N  CB       7  N   N   Y  AT&T              PRINCESS AS 550 Z-71322 
PA  N  CB       3  N       Y  AT&T              SPKK REMOTE & ANS MACHINE 
PO  N  AM   50000  Y   Y      AT&T              SW204 
BM  N  FM   16000  Y   N   Y  AT&T              TRIMLINE 210 
BF  Y  AM   50000  N       Y  AT&T              TRIMLINE 210 
DL  N  CB       5  Y       Y  AT&T              TRIMLINE 220 
NF  N  AMA   1500  Y   Y   Y  AT&T              TRIMLINE AS550Z-71597-T 
ST  N  AM   10000  Y   N   Y  AUDIOVOX          AT-11 
PO  N  AM   50000  Y   N      BELL              FAVORITE 
PL  N  AM    5000          Y  BELL              TT-51490 
KI  N  CB       5  N          BELL PHONES       100-5800 
AT  Y  CB     160  N   N   Y  BELL SOUTH        2000 
BS  N  AM   50000  Y   N      BELL SOUTH        227V 
DT  N  CB       3             BELL SOUTH        473 
KI  N  CB       5  N          BELL SOUTH        473 
DS  N  AM    5000          Y  BELL SOUTH        473 
MA  N  AMA    600             BELL SOUTH        CWIMLA-61669-ANN 
OR  N  AMA    100  N   Y      BELL SOUTH        DPK-62W70687-TE-T 
AT  N  IB  500000  N       Y  BELL SOUTH        HAC 572 
PS  Y  AMA    150  N   N   Y  BELL SOUTH        TP-201 L-10 
SF  N  AM   50000  Y          CANON             FAX-350 
PO  Y  AMA    500  Y          CODE-A-PHONE      1610 
LA  Y  AM   50000  N   N      COMDIAL           25270-IY 
SF  N  AM   50000             COMDIAL           VOICE EXPRESS 
ST  N  CB      75  N   N   Y  CONAIR            PR 1000 
AT  Y  CB          Y       Y  CONAIR            PR 5001 
LV  N  CB      57  N   N      CONAIR            SW 2502 
TP  N  CB       5             CONAIR            SW204 
BE  N  AMA     80      N      CONAIR            SW204A 
PO  N  AM   50000  Y          CONAIR            TR101 
AN  N  FM   51000  Y   Y      CONAIRPHONE       PR1006 
PO  Y  AMA    500  Y          CONAIRPHONE       PRIMA SERIES 
DT  N  CB       3  N   N   Y  CONAIRPHONE       SW-102 
HL  N  AM   10000             DELTA             HEK-EB-200DSIHF-EXT 
SD  N  CB      12  N          FORTEL CORP       RECORD A CALL #2140 
SF  N  CB       2  N   N      GENERAL ELECTRIC  12-MEMORY 2-9240A 
PO  N  AM   50000  Y   N      GENERAL ELECTRIC  2-9051LRA 
MA  N  CB       6  N          GENERAL ELECTRIC  2-9166B 
CG  N  AM   50000  Y       Y  GENERAL ELECTRIC  2-9166B 
TP  Y  CB       4  N       Y  GENERAL ELECTRIC  2-9167A 
KC  N  CB       2  Y       Y  GENERAL ELECTRIC  2-9212BLB 
LV  Y  CB       4  N   N      GENERAL ELECTRIC  2-9243 
DT  N  AM     438             GENERAL ELECTRIC  2-9243C 
KC  N  FM    8000  N          GENERAL ELECTRIC  2-9355A 
LV  Y  CB       5  N   N      GENERAL ELECTRIC  2-9356 
VB  N  AMA    100  Y          GENERAL ELECTRIC  2-9400C 
HL  N  FM   54000             GENERAL ELECTRIC  2-94050A 
HL  N  FM   54000             GENERAL ELECTRIC  2-94050A 
HL  N  FM   54000             GENERAL ELECTRIC  2-94050A 
HL  N  FM   54000             GENERAL ELECTRIC  2-94050A 
MA  N  CB       6  N          GENERAL ELECTRIC  2-9420A 
HU  N  FM  100000  N          GENERAL ELECTRIC  2-9675A 
PS  Y  CB       5  Y   Y   Y  GENERAL ELECTRIC  2-9892A 
DV  N  CB       2  Y   Y   Y  GENERAL ELECTRIC  2-9895A 
LV  N  CB       4  N   N      GENERAL ELECTRIC  29270 A 
DV  N  AM    5000  Y          GENERAL ELECTRIC  7-4700A 
LA  N  AM    5000  Y   Y      GENERAL ELECTRIC  CRYSTAL CLEAR PLUS 
BF  N  CB       5  N       Y  GENERAL ELECTRIC  MEMORY MODEL 21 
MA  N  CB       6  Y          GENERAL ELECTRIC  NO 29420A 
SD  N  CB      54  N   N      GENERAL ELECTRIC  SPEAKER PHONE 2-9375F 
CG  N  AMA   1500             GENERAL ELECTRIC  TL-5/TPS 
PO  N  AMA     35  Y   N      GTE               58821 
ST  Y  FM   51000  N   N   Y  GTE               7400 
GI  N  AMA    101  Y          GTE               AUTO ELEC - WALL PHONE 
GI  N  AMA    101  Y          GTE               AUTOMATIC ELECTRIC 
PL  N  AM    5000      N      IMA               (NONE) 
AL  Y  AM    5000  N   N   Y  ITT (CORINTH      3480 FEATURE TELEPHONE
                              TELECOM. CORP)    
DS  N  FM    3000  Y   N   Y  LENOX SOUND       P4316 
PL  N  AM    5000             LLOYDS (PHONE-    T510
                              CLOCK-RADIO) 
HU  N  CB     110  N          LONE STAR         912 
PA  N  CB       4          Y  LONE STAR         TRIMLINE 
BS  N  CB       5  N   N      LOTEL             5020 DUEL LINE 
BS  N  CB       5  N   N      LOTEL             5020 DUEL LINE 
FE  N  AMA    131  N          NORTHERN TELECOM  FCC REG #AB6982-68817-TE-T 
AN  N  FM   51000  Y   Y      NORTHERN TELECOM  NT3L00AA 
DT  Y  CB       5  Y   N   Y  NORTHERN TELECOM  SYMPHONY 3000 
PS  N  AMA    200  N   N   Y  NORTHWESTERN BELL "EASY TOUCH" 
SD  Y  CB      12  N          NORTHWESTERN BELL BASIC TGT 51450 
LV  N  CB       4  N   N      PAC BELL          TR 2203 CHAC 
PO  Y  AM   50000  N   N      PACTEL            FE5700 
DS  N  AMA    500  N   Y      PANASONIC         EASA-PHONE VA-8205 
NY  N  AMA    100  Y   Y      PANASONIC         EASA-PHONE-AUTO LOGIC 
BS  N  AM   10000  N   N      PANASONIC         EASE PHONE KX-TX175-B 
TP  Y  CB       3  N   N   Y  PANASONIC         KX-T-2420 
SF  Y  AMA    250  Y   N      PANASONIC         KX-T-3155 
DV  N  AMA    114  N   Y   Y  PANASONIC         KX-T2315 
DL  N  CB       4  Y   Y   Y  PANASONIC         KX-T2315 
PO  Y  AM   50000  Y   Y      PANASONIC         KX-T2355 
CG  N  AMA   1500  N       Y  PANASONIC         KX-T2355 
ST  Y  AM   10000  N   N   Y  PANASONIC         KX-T2622 EASAPHONE 
HL  N  AMA    462             PANASONIC         KX-T3145 
OR  N  AM   50000  N   Y      PANASONIC         KXT 2388 
KI  N  CB       5  N          PHONEMATE         3900 
NF  N  CB       7  Y   N   Y  PHONEMATE         3950 
GI  Y  AMA    101  N          PHONEMATE         4650 
BS  N  AM   10000  N   N      RADIO SHACK       209 DUCPHONE 43-617A 
DS  N  FM    3000          Y  RADIO SHACK       43-384 
PS  Y  CB       5             RADIO SHACK       43-384 
DT  N  CB       3          Y  RADIO SHACK       43-625 DUOFONE 202 
TP  Y  CB       4  N       Y  RADIO SHACK       43.430 
PO  Y  AM   50000  Y   N      RADIO SHACK       DUOPHONE TAD-250 
OR  N  CB       4  Y          RADIO SHACK       ET 200 
LR  N  CB          N          SANYO             TA S 855 
AT  N  CB     160  N       Y  SEARS             3293 4761550 SR 3000 
KI  N  FM    3000  N          SEARS             34403 
DL  N  AMA    800  Y   Y   Y  SEARS             34505 
LV  N  CB       4  N   N      SEARS             SR-2000 
KI  N  FM    3000  N          SOUND DESIGN      7255 AR 
TP  Y  CB       3  N   N   Y  SOUNDESIGN        7339 IVY 
NY  Y  AMA    100  Y   Y      SOUTHWESTERN BELL FCC 2555 
BE  N  CB       4      N      SOUTHWESTERN BELL FREEDOM PHONE 
ST  Y  CB      75  N   N   Y  SOUTHWESTERN BELL FREEDOM PHONE FC 2570 
BS  N  AM   10000  Y   N      SOUTHWESTERN BELL FT-325 
SF  N  AM   50000             STROMBERG         IMAGE 1 AND IMAGE 2 DTMF 
ST  Y  FM   51000  N   N   Y  TECHNICO          TT-2201 
SJ  N  CB      26  N       Y  TELEFONICA        TXE-1
                              HISPANO AMERICAN  
SJ  N  CB       7  N       Y  TELEFONICA        TXE-1
                              HISPANO AMERICAN 
TP  N  CB       3  N   N   Y  TELKO             221 
ST  Y  CB       4  N   N   Y  THOMAS            PP9D NOSTALGIA PHONE 
FE  N  AM   50000  Y          TIME LIFE (MADE   (NONE)
                              IN TAIWAN) 
DS  N  AM    5000  Y   Y   Y  TISONIC           PT-91 
LV  Y  CB       5  N   N      ULTRSONIC         019 
KC  N  FM    8000  N          UNIDEN            TRIMLINE 
FE  N  AM   50000  Y          UNISONIC          (NONE) 
AL  Y  AM    5000  N   N   N  UNISONIC          (NONE) 
VB  Y  CB      30  Y          UNISONIC          6434 
BM  N  CB       4  N   N   Y  UNISONIC          9370 
PL  Y  AM    5000  Y   Y   Y  WESTERN ELECTRIC  (NONE) 
DT  N  AM     438  Y       Y  WESTERN ELECTRIC  (NONE) ROTARY DIAL PHONE 
DT  N  AM     438             WESTERN ELECTRIC  (NONE) ROTARY DIAL PHONE 
NF  N  AMA   1500  Y   Y   Y  WESTERN ELECTRIC  AS543M-62587-TE-T 
PA  N  AMA    110  N       Y  WESTERN ELECTRIC  CS 2500 DMG 84121

fo=Field Office,fil=filter already installed? ix=Service causing 
interference power=power of transmiter att=Problem corrected with
AT&T Z100-B1? oth=Problem corrected with other filter? 
fcc=Problem corrected with FCC "bullet-proof" phone?

                               ATTACHMENT 3

                          FIELD OPERATIONS BUREAU
                       TELEPHONE INTERFERENCE SURVEY
                  TELEPHONES NOT RECEIVING INTERFERENCE

 
off  filter  make               model
           
NF     Y     AT&T               1316C 
DL     N     AT&T               1321 
SF     N     AT&T               1323 
NY     N     AT&T               5200 
SF     N     AT&T               5200 
BF     N     AT&T               5400 
ST     N     AT&T               5600 
PA     N     AT&T               60921 
CG     N     AT&T               700 
ST     N     AT&T               730 
PA     N     AT&T               ANS MACHINE 
PA     N     AT&T               AS5 THA-60921-MT-E 
DL     N     AT&T               CS8702A 
DL     Y     AT&T               NE-229A 
OR     N     AT&T               OLD DIAL STYLE 
BF     Y     AT&T               TRIMLINE 
BM     N     BELL SOUTH         665 CORDLESS PHONE 
HU     N     BELL SOUTH         HAE-701 
OR     N     BELL SYSTEM        TRIMLINE 
AL     N     COBRA              AN-8519 
DT     N     COBRA              ST-410 
SD     N     CODE A PHONE       8100 
AL     N     CONAIR CORP        XS2400 
LV     N     CONAIR             CORPORATE AMERICA 
BS     N     DAK INDUSTRIES     DAL-4000 AX 
NF     Y     DAK INDUSTRIES     DK 4000 AX 
CG     N     GANDALF            COMDIAL 
AL     N     GENERAL ELECTRIC   2-9051LRB 
KC     N     GENERAL ELECTRIC   2-9800B 
BM     N     GTE                (UNKNOWN) 
ST     N     GTE                980 SLIMLINE 
PS     N     ITT                183499-236 
FE     N     ITT                500D 
AN     N     ITT                RJ11C 
AL     N     LENNOX SOUND       PH-319 
HL     N     UNKNOWN (CHINA)    FCC #: GEZ 364-16521 TE-E 
HL     N     NORTHERN TELECOM   SYMPHONY 1000 
DV     N     NW BELL            FAVORITE PLUS DHT6CJ-14584-TE 
BS     N     PANASONIC          EASE PHONE-ONE LINE 
HU     N     PANASONIC          GASA-PHONE 
DV     N     PANASONIC          KX-T-3120 
HL     N     PANASONIC          KXT-2355 
KC     N     PHONEMATE          4300 
ST     N     RADIO SHACK        43-368A 
FE     N     RADIO SHACK        43-500 
FE     N     RADIO SHACK        43-5018 
DV     N     RADIO SHACK        43-621 
OR     N     SEARS              329 34451750 
DT     N     SEARS              34413 
GI     N     SEARS              HAC 3466 
ST     N     SEARS              SR 3000 SERIES 
SF     N     SHARP              UX-172 
SF     N     SOUND DESIGN       AM/FM CLOCK RADIO PHONE 
AL     N     SPECTRA PHONE      TL-4 
DT     N     STC TELECORP INC   SOUNDDESIGN 7255 
ST     N     TELECONCEPTS       (NONE) 
NF     N     WESTERN ELECTRIC   (UNKNOWN) 
BM     N     WESTERN ELECTRIC   (UNKNOWN) 
DL     N     WESTERN ELECTRIC   (UNKNOWN) 
KC     Y     WESTERN ELECTRIC   (UNKNOWN) 
LA     N     WESTERN ELECTRIC   "LA OLYMPIC PHONE" 
PA     N     WESTERN ELECTRIC   2554 BMPG-82103 
BS     N     WESTERN ELECTRIC   RB 1311 (ROTARY) 
NF     Y     WESTERN ELECTRIC   TRIMLINE #CS 2224A 
NF     N     WESTERN ELECTRIC   TRIMLINE PHONE

                               ATTACHMENT 4

                          FIELD OPERATIONS BUREAU
                       TELEPHONE INTERFERENCE SURVEY
                           OTHER FILTERS TESTED


                       K-COM RF-1                  1
                       K COM RF1                   3
                       RADIO SHACK-SNAPON          1
                       TCE                         1
                       TCE536                      2
                       TCE TP12                    4
                       TEC RF1400                  2
                       TII 931-W1                  2

 
The filters listed here deserve further study.  During the 
project, FOB found that these filters eliminated interference when 
tried in individual cases.  However, because FOB did not use any 
of these filters in a sufficient number of cases, we cannot 
conclude whether any of them would be effective in eliminating 
interference most of the time.


                               ATTACHMENT 5

                          FCC BULLET PROOF PHONE

 
Manufacturer                       Make                  Address

 
Pro Distributors              Western Electric       2811 74th Street, 
                              Desk Model             Lubbock, TX
                              Touch Tone             1-800 (658-2027)

 
TCE Labs                                             2365 Waterfront Park Drive
                                                     Canyon Lake, TX 78133
                                                     800-KILL-TVI (545-5884)
                                                     210-899-4575

Note: All phones were refurbished, internally modified commercial units.

