Evening star., 1927-04-17

If a new crystal detector recently
patented as a telephone attachment
is put on the market many fans may
return to the delightfully."- clear re-
ception and simplicity of operation
afforded by the first type of radio
receiver Literally it amounts to a
pocket crystal receiving set or ii
desired, an adjustable and perhaps
more efficient tube receiver, which
may be attached to any desk tele-
phone and used to listen to local
broadcasts. utilizing the regular
telephone receiver.
Patent No. 1,622,335, issued to G.
F.. Mitchell of Washington and as
yet unassigned, covers simple
means of constructing q crystal radio
receiver readily attachable to an
ordinary telephone. Its use may de-
pend, however, upon securing the
permission from local telephone com
panies. An examination of contracts
may prevent its general use, al
though it is said not to interfere
with the ordinary use of the phone
The device is exceedingly interest
ing, compact and simple. 1t carries
out the scheme of using the lines OF
the telephone company as an aerlal
for broadcast reception, but in addl-
ton, permits the use of the telephone
ear piece itself. It's adoption elimi-
mates, therefore, the need for an
aerial, head phones. extra wiring or
any modification of the telephone cir
cult beyond simple connections with
the conductors. 1t is portable and
adjustable to any phone in few
seconds, apparently without inter-
fering with normal telephone oper-
alton.
The apparatus consists of a hollow
box or housing, about the size of the
vertical piece of ordinary telephone
standard, to which it is attached by
three spring clips. The back of this
housing is made Of insulating mate
rial, A contact strip from the top OF
| the housing member engages with
and makes electrical contact with
| the top of the phone stand. Mounted
| on top this housing is an adjustable
crystal rectifier, connected by wires
| inside the housing to terminals. On
| one side of the housing is mounted
Ia mechanical latch which, when en-
gagged, prevents the rising of the
| telephone switch or hook when the
receiver is lifted and used to listen
in on broadcasts picked up by the
| telephone wires. When this latch is
tdisengaged the telephone may be
used in the ordinary way for con-
IsversaAion4 AS in a simple crystal re-
ceiver circuit, the regular telephone
receiver, or if desired. pair of ear
phones, is connected across the de-
tector which is placed between the
aerial and ground connections. An
other possible connection permits the
shunting of a pair of ear phones by
means of condenser and the utili-
cation of a tuning inductance placed
inside the hollow housing shaft. MIR.
Mitchell explains in his patent speci-
| hcations how an electron tube cir
cult may also be adapted where
variable tuning condenser, miniature
tubes and practically all the feature.
| of a tube set are all placed within
| the housing. member.
One means of establishing contacts
with the phone wires is by special
| flexible connecting wires tipped with
pin points for thrusting through the
cord leading to the telephone receiver
so as to put it in the output circuit
of the radio receiving apparatus while
another wire is used for a ground
contact. Another adaptation provides
| for a more permanent connecting
system, comprising a pair of sockets
and a two-pronged plug. probably to
| be provided by the telephone COM
pony in the base of the phone stand
| for these connections.