Telephone Eavesdropper

An advanced amplifier with line output

Galvanic isolation is a special feature of this telephone amplifier, which includes a line output connection for a hi-fi system.
Although in some countries, including the UK and Germany, analogue telephone connections are something of a dying breed, most residential customers use analogue apparatus, even in cases where the underlying connection is over ISDN.

This is a MEMBER ONLY article. You need a subscription to read this article.

Benefits of a subscription

Unlimited access to online Member Only articles
3 new editions Elektor Magazine (digital)
More than 5000 Gerber files
20% member discount on e-books (at elektor.com)
10% member discount on Products (at elektor.com)

View the offers
Available from €5.33 per month.

What is Elektor Exclusive?

Materials

030379-PCB.pdf

Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends the Elektor PCB Service service from its business partner Eurocircuits or AISLER as the best services for its own prototypes and volume production.

The use of our Gerber files is provided under a modified Creative Commons license. Creative Commons offers authors, scientists, educators and other creatives the freedom to handle their copyright in a more free way without losing their ownership.

PCB

Download Gerber file: 030379-1.zip

Component list

Resistors:
R1,R3 = 10k?
R2 = 8k?2
R4 = 100k?
R5,R6,R11 = 1k?
R7 = 220?
R8,R12 = 3k?3
R9 = 2?2
R10 = 2k?2
P1 = 250k? preset H
P2 = 10k? logarithmic potentiometer, mono
Capacitors:
C1 = 2µF2 63 radial
C2 = 15nF 400V
C3 = 1nF 400V
C4 = 68pF
C5,C16,C18 = 10µF 63V radial
C6,C10,C15,C17 = 100nF
C7 = 220µF 16V radial (max. diameter 8mm)
C8 = 1nF ceramic (5mm lead pitch)
C9 = 330nF
C11,C12,C13 = 470µF 16V radial (max. diameter 8mm)
C14 = 3nF3 (5mm lead pitch)
Semiconductors:
D1,D2 = BAT85
D3 = LED, low current
D4 = 1N4002
IC1 = LF356
IC2,IC3 = 6N138 (Farnell # 325-831)
IC4 = TDA7052
IC5 = NMV0512SA, C&D Technologies/Newport Components (Farnell # 589-822)
IC6 = 7806
Miscellaneous:
K1,K2 = RJ45 socket
LS1 = 8 ? / 1W miniature loudspeaker
Solder pins
PCB, order code 030379-1