Line Switcher

A single phone for two lines

Published in issue 371, November 2007

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)
K2 = 2-way SIL pinheader for power: 9 V NiMH battery
S1,S2 = pushbuttons
RE1 = Bistable 5 V 2-pole c/o relay (Panasonic DS2E-ML2-DC5V or Omron G6AK-234P-ST-US)