| |
G8MNY > TECH 10.10.14 11:37l 171 Lines 6744 Bytes #999 (0) @ WW
BID : 12173_GB7CIP
Read: GUEST
Subj: A Simple Telephone Tester
Path: IW8PGT<IV3ONZ<IZ3LSV<I0OJJ<GB7CIP
Sent: 141010/0903Z @:GB7CIP.#32.GBR.EURO #:12173 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated May 13)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Ever needed to test the functions of a pair of Phones Answering machine, FAX,
Modem etc. without 2 telephone lines? This is a simple tester I knocked up in a
dual phone socket, plus a plug top PSU, to mimic most telephone line functions.
FEATURES
PHONE 1 "off hook" can listen to dial tone
Manual ringing of PHONE 2
PHONE 2 "off hook" removes dial tone from PHONE 1
PHONE 1 "on hook" causes line reversal to PHONE 2 (release the call test)
Variable line loss
Line status LED indicators
PLUG TOP PSU
ÚÄÄÄÄÄÄÄÄ2k2ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ>Ringing drive
³
L¿ Ú¿ ÚÄÄÄÄÂÁÄ´>ÃÄÂÄÄÄÄÂÄÄÄÄÄÄÄÂÄÄÄÄÄ¿+60V
³ o )||( ³ ³ ³ 1k ³/
³ | )||( À´<ÃÄÄÄ)Ä¿ ³ ÃÄÄÄ´ T1 4 way cable
ÀÄo )||( 36V ³ ³ === _³_ ³\e
)||( Ú´>ÃÄÄÄÙ ³ ³470u /_\' ÀÄÄÄÄÄ>+50V (@ 40-80mA)
)||( ³ ³ ³100V ³50V
NÄÄÄÙ ÀÄÄÄÄÁÂÄ´<ÃÄÄÄÁÄÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄ>0V
heat fused ³
Transformer ÀÄÄÄÄÄÄÄÄ´ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ>Dial Tone
u1
100V
The 50V 1W zener is actually series of zeners, T1 is any 200mA 100V 2W NPN.
The transformer's AC voltage in not high enough to ringing a phone directly, so
it is used to drive a line reversing relay to make the ringing.
A small u1 capacitor takes off some of higher harmonics of the AC to mimic dial
tone.
TEST CIRCUIT
+50V>ÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄ¿
_³_ ³ ³ _³_
LED 1=\_/ ³ ³ \_/=LED 2
³ 1k5 1k5 ³
Ringing>ÄÄÄÄÄo o 1W 1W ³
drive RING / SW ³ ³ ___³___
___³___ ³ ³ ³RELAY 2³
³RELAY 1³ ³ ³ ~~~³~~~
~~~³~~~ ³ ³ ³
RING \ SW ³ ÃÄÄ2k2ÄÙ
o oÄÄÄÄ2k2ÄÄÄ´ u47 ³
³ ³ 100V 4k7 ³ relay 1
ÚÄ)ÄÄÄÄÄÄÄÄÄÄÄÄÁÄ\ oÄ´ÃÄÄVARIABLEÄÁÄÂÄÄo o¿
³ ³ relay 2 o line loss ³ \ ³
Calling 2<ÄÙ ³ ³ ³ ÀÄ)ÄÄÄÄ>2 Answering
PHONE 1 ³ Dial tone>ÄÄÄÙ ³ ÚÄÄÄÄÙ PHONE 2
Socket 5<ÄÄÄ´ ³ ³ ÚÄÄÄÄÄÄ>5 Socket
ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ)ÄÁo/ o
³ ÀÄÄÄÄÄÙ
0V>ÄÄÄÄÄÄÙ relay 1
Both relays are double changeover (only 1 needs to be) 28V 7mA DIL type, with
4k coil resistance, note some types may have internal diodes so polarity may
matter! During ringing RELAY 1 has to operate & release 50 time a seconds to
deliver +/- 50V to PHONE 2 to look similar to the 75V AC (17-25Hz) + 50V DC of
real telephone ringing.
The manual RING SWitch is a non locking double pole changeover.
Line loss & matching is all approximate, like the real world nothing is 600ohm!
But using 600 ohm test gear & blocking the DC etc. actual line losses could be
calibrated on the variable resistor scale (e.g. 10-30dB Max). A more realistic
dummy line & noise sources could be used as the middle section if it was
important (e.g. for a high speed modem evaluation).
REAR VIEW LAYOUT
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ()LED LED() ³ The PCB is removed from the case by heating the
³ ÚÄ¿ 2 1 ÚÄ¿ ³ melted spigots (with a soldering iron).
³ ³R³ 1k5 1k5 ³R³ ³
³ ³L³ ³L³ ³ The PCB needs links cutting to isolate the 2 lines
³ ³1³ 4k7 u47 ³2³ ³ if it is a shared phone socket type. The PCB at
³ ÀÄÙ_____ _____ÀÄÙ ³ the switch location is cut away & it is mounted in
³o) ³_____³ ³_____³ (o³ a drilled front case hole. Tight holes in the case
³ PHONE 2 PHONE 1 ³ are also made for the LEDs who's wires poke new
³ ³ PCB holes.
³ ³
³ ÚÄ¿RING [] ³ After testing reassemble & reheat anything left of
³ ³ ³SW [] ³ the spigots or use some glue.
³ ÀÄÙ [] ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
In UK jack pins 2 & 5 are the 2 wire line, & a 3rd wire may be used for the
phones ringer path via a master socket capacitor. See your local telecomms Co.
(POTS) arrangements if different from UK.
PHONE CALL SIMULATION
1/ Connect 2 PHONE devices.
2/ Lift PHONE 1, LED 1 lights up, listen to buzzing dial tone & U have "Blow".
3/ Intermittently operate ringing switch (concadance ringing).
4/ Does PHONE 2 ring? (LED 2 lights dimly to ringing) Can it answer the call?
5/ On answer, LED 2 lights, PHONE 2 has "Blow", & PHONE 1 dial tone disappears
& a transmission path to PHONE 2 is made.
6/ Can you talk or send data both ways over transmission paths, is loss OK?
7/ Clear down PHONE 2, LED 2 goes out, & dial tone is returned to PHONE 1.
8/ If you cleared down PHONE 1 first instead, then PHONE 2 gets a line
polarity reversals, which should cause automatic kit to hang up & clear the
line for the next call. I found some kit just times out instead!
REAL PHONE TONES
DTMF-Telephone Standards Touch-Tone dialing
Touch-tone was a registered trademark of AT&T. It is also known as dual-tone
multiple frequency (DTMF) signaling!
The two tones in a 4 x 3 keypad matrix, a low-frequency tone & a high
frequency tone, to specify 1 of the 16 options. Pressing 2 keys in the same
row/column, normal results in a single tone. The 2 tones must not clip & mix
as the DTMF Rx IC uses the presence of more than 2 tones the identify the
signal non DTMF & ignores it.
TONE HIGH 1209Hz 1336Hz 1477Hz (1633Hz)
LOW
697 Hz 1 2 3 (A)
770 Hz 4 5 6 (B)
852 Hz 7 8 9 (C)
941 Hz * 0 # (D)
Level each tone: -6 to -4 dBm
Maximum difference in levels: 4 dB
Maximum level (pair): + 2 dBm
Frequency tolerance: ñ 1.5%
Pulse width: 50 msec
Time between digits: 45 msec minimum
DIAL TONE: 350-440 Hz
BUSY TONE: 480-620 Hz, with 60 interruptions per minute
EQUIPMENT ENGAGED TONE: sounds like busy tone, but slighjtly different!
RINGING TONE: 440-480 Hz, 2sec on, 4sec off
RINGING VOLTAGE: 17-22Hz 75V AC to earth & -50V DC. (155V peak!)
(cacadance) Load AC 1000ohms via a 1.8/0.9uF.
LINE CURRENT: Around 50mA, typically 10V across a phone in use.
Why Don't U send an Interesting Bul?
73 de John G8MNY @ GB7CIP
Read previous mail | Read next mail
| |
