Line Switcher
A single phone for two lines
More and more ISPs, are offering subscribers an extra phone line using Voice over IP (VoIP) on top of their Internet access.
The project described here reduces this inconvenience by letting you connect a single phone to two lines at once, to avoid having to tie knots in the cables! It’s a phone line switcher that routes the ‘correct’ line to the phone automatically.Materials
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.
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Component list
Resistors
R1,R2,R7,R8 = 33k
R3,R11,R18 = 10k
R4,R13,R27 = 1M
R5,R6 = 100
R9,R10 = 100k
R12 = 4MΩ7
R14,15 = 47k
R16,R17,R21,R22,R25,R26 = 1k
R19,R20 = 100k
R23,R24 = 470k
Capacitors
C1–C4 = 100nF (7.5mm pitch MKT)
C5 = 470 nF (7.5mm pitch MKT)
C6,C9 = 6μF8 100 V
C7,C8 = 10μF 100 V
C10,C11 = 220μF 10V non-polarised
C12,C13 = 10nF (5mm pitch Sibatit/ceramic)
C14,C15 = 100nF (5mm pitch Sibatit/ceramic)
Semiconductors
D1,D2 = BAT85
D3,D4 = 1N4148
D6,D7 = LED, 3mm, green (low power)*
D5,D8 = LED, 3mm, red (low power)*
T1,T2 = BC557
T3–T7 = BC547
IC1 = 40106BF
IC2 = 4093
IC3–IC7 = TLP620 (Toshiba optocoupler)
Miscellaneous
K1,K3,K4 = RJ11 6/4 phone socket (Hirose TM5RE1-64)
S1,S2 = pushbuttons
RE1 = Bistable 5 V 2-pole c/o relay (Panasonic DS2E-ML2-DC5V or Omron G6AK-234P-ST-US)
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