MATERIALS AND TOOLS
1930s-era desk telephone » Available through
eBay, thrift stores, antique stores, and the
like. These phones have big components and
everything screws together, making them
very easy to work with. Look for one with
fabric-covered cords.
USB VoIP telephone, aka Skype phone » can be
found for $25 or less online. I used a CM-01
VoIP Handset from
ebay.co.uk seller shop4usb.
12V power supply » aka power adapter,
aka wall wart
Electrical tape »
Cable ties, small »
Screwdriver, flathead »
Pliers »
Wire cutters and strippers »
Multimeter »
Soldering iron with a fine tip »
Solder »
Desoldering braid » or solder sucker
Glue gun and hot glue »
FOR THE HANDSET CONVERSION
USB-powered speakers » with a headphone jack;
not USB speakers that also receive signal via
USB. $25 or less at drug and discount stores.
Network cable, CAT5e » #278-1764 from
RadioShack (
radioshack.com), $10
Voltage regulator, 7805 or 78M05 » #276-1770
from RadioShack, $2
Small, short screw » like a PC motherboard
mounting screw, M3 or 6-32
Machine screw and nut » for mounting voltage
regulator. The screw should fit through a
3.5mm hole.
Woven mesh tubing (optional) » to replace original
handset cord if it’s difficult to extract wires
FOR THE RINGER CONVERSION
Arduino » I used a Duemilanove, but the newer
Uno would also work, item #MKSP4 from Maker
Shed (
makershed.com), $35. You could also
use a Nano, #MKGR1 from Maker Shed, $35,
but see Final Notes.
Network cable, CAT5e » another one, 2 total
needed for both handset and ringer conversions
Transistors, TIP120, TIP110, NTE261 or similar ( 2) »
#276-2068 from RadioShack, $2
Resistors, ¼W or ½W: 1k » Ω ( 2), 10kΩ ( 1)
#271-1321, #271-1335 from RadioShack,
$1 per 5-pack
Project box, small » An Arduino-sized box like
#PRT-10088 from SparkFun Electronics
(
sparkfun.com), $12, would look nattiest, but
I just used a black ABS enclosure I had handy.
Diodes, 1N4002 or similar ( 2) » #276-1653 from
RadioShack, $3 per 25-pack
Heat-shrink tubing » #278-1610 from
RadioShack, $4
48 Make: Volume 25
speaker. To obtain these wires, carefully cut away
the outer sheath from a CAT5 networking cable and
remove 2 twisted wire pairs.
Fabric-covered handset cords are the easiest to
modify without altering the phone’s appearance.
Some have 4 strands braided together, but only 3
contain wires; the fourth is cotton. With these cords,
disconnect them from the handset and unbraid
them all the way to the base. Pull the original wires
out of 2 cords, and snake the twisted pairs through,
leaving extra wire at each end. Braid the strands
back together (4-strand round-braid instructions
are at
makezine.com/go/braid) and run them back
into the handset (Figure G, previous page).
With one-piece cords, try to pull the wires out
of the outer sheath. If that isn't possible, you may
need to compromise authenticity by substituting
a different wire cover like Tech-Weave. As with the
fabric cord, leave the twisted pair long at each end
and run the cord back to the handset (Figure H).
Inside the handset, connect one wire pair to the
microphone and the other pair to the speaker. To
determine which pair of contacts connects up to
the speaker, you may be able to follow the wires
visually. If it isn’t obvious (or if you want to confirm),
you can use a multimeter. Look for a resistance of
about 36Ω across 2 of the contacts.
With the phone in Figure I, I used pliers to remove
a metal pin behind the microphone, severing the
connection between mic and speaker. With the mic
wire pair, I attached one wire to the back of the
microphone and the other to the screw mount for
the metal spring that the mic pushes against. One
speaker wire screwed into the newly vacant pinhole behind the mic using a PC motherboard screw,
and the other to a nearby screw that I determined
ran up to the speaker.
With a hollow handset, you can simply run the
twisted pair for the speaker up through the handset
and connect it directly (Figure J).
With these 4 connections in place, reassemble
the handset.
2.CONNECT HE USB PHONE
Break open your USB telephone’s case to expose its
main circuit board, which is basically a sound card
(Figure K). Locate and desolder the points on the
card where the phone’s microphone and speaker
connect. Strip the free ends of the wire pair from
the vintage handset’s microphone, and solder them
to the sound card’s mic contacts (Figure L).
