Voice path tester
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Purpose:
The Voice path tester (VPT) can be used to test the voice (and data) path
of a telecommunications network, PBX, or anything else that has an
interface for a standard telephone handset.
Usage:
The VPT produces a signal which is injected into the network
under test via the handset socket. Configure the network so that the
signal is looped back at the far end. Having travelled around the network,
the signal re-enters the VPT where it can be listened to on the internal
speaker (or headphones). The output from the VPT and the signal coming back
from the network can be monitored and compared using an oscilloscope.
The frequency (approx 30hz-18 Khz) and amplitude of the generated signal
can be selected. (Note that telecomms networks normally do not pass any
frequency above 4Khz) . The signal output is selectable as a sine, triangle
or square wave, or an external input can be used. The external input can be
connected to a PC and used to play in recorded sounds. DTMF tones are one
use of this facility.
Applications:
1. Connected to the handset socket of a phone.
2. Connected to the handset socket of an SDH/SONET/T1/E1 test set.
The schematic was created with Eagle.
Links:
CadSoft Eagle Schematic & Layout Editor Windows/Linux
(Free for non-commercial use)
http://www.cadsoft.de
DTMF dialler software for Windows (Free)
http://www.silverstones.com/DTMFdial.htm
Farnell Electronic components. (not free unfortunately)
http://www.farnell.com
Voice path tester
Part numbers from Farnell: http://www.farnell.com/
Part Qty Part No. Cost (approx)
Enclosure x1 301-360 3.53
Feet for enclosure x1 148-922 5.03
PSU x1 200-918 36.59
Power socket pnl mnt x1 224-972 3.92
Prototyping board x1 967-397 11.96
BNC socket 50 ohms, pnl mnt x2 583-510 1.74
LED bezel mnt blue x1 882-872 2.88
Speaker x1 453-109 3.63
FCC-68 socket x1 151-584 0.94
3.5 mm jack socket x2 143-336 1.95
6 pole rotary switch x1 140-513 14.88
Stop screws for switch x1 678-387 0.09
Knob for switch, 4mm shaft x1 320-390 1.84
Cap for knob pk5 x1 320-845 0.24
Pot 1K panel mnt x1 350-047 0.77
Pot 10K panel mnt x1 350-072 0.77
Pot 10K log panel mnt x1 350-175 0.86
Knobs for pots x3 143-281 1.20
1 K pot PCB mnt multiturn x1 238-119 3.73
100 K pot PCB mnt multiturn x1 346-445 0.69
10 M pot PCB mnt pk5 x1 643-191 0.19
Audio amp IC ST TDA2822M x2 410-767 1.00
Func IC Intersil ICL8038CCJD x1 405-530 5.60
220 uF cap x4 661-030 2.18
100 nF cap pk10 x1 146-232 0.26
4.7 nF cap pk5 x1 108-945 0.33
470 uF capacitor x1 661-144 3.89
1 K resistor pk50 x1 509-164 0.01
1.5 K resistor pk50 x1 509-188 0.95
33 ohm resistor pk50 x1 508-986 0.95
20 K resistor pk50 x1 770-772 0.01
4.7 K resistor pk50 x1 509-243 0.01
4.7 ohms resistor pk50 x1 508-883 0.01
15 K resistor pk50 x1 509-309 0.01
620 ohm resistor pk50 x1 770-590 0.95
1N457 diode x1 884-984 0.11
Also required to prepare enclosure:
Set of drill bits
Set of needle files
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