Shure 718A User Guide
SHURE BROTHERS
Microphones and Acoustic Devices
225 WEST HURON STREET :: CHICAGO 10, ILLINOIS
PHONE Delaware 7-4550 :: CABLE: SHUREMICRO
INCORPORATED
DATA SHEET
DATE: FEBRUARY, 1947
SUBJECT: Model 718A "Versatex" The
Versatile Crystal Microphone.
Model 718A "Versatex" The
General: Model 718A "Versatex" is an extremely
versatile pressure-operated diaphragm type crystal microphone. The "Versatex" is suitable for placement on table
top, desk top, or other flat surface; it fits conveniently in
the palm of the hand for use as a hand microphone: it is
provided with a 5/8"-27 Thread and may be used on a
conventional floor stand. The "Versatex" has the typical
semi-directional properties.
The crystal used is a Bimorph unit with special-pro-
cess moisture proofing.
The microphone is provided with a built-in protective
resistor to give increased protection against Radio Frequency burn-outs when used with radio transmitters.
The Model 718A "Versatex" is supplied with a jr-foot
shielded plastic-jacketed cable.
Applications:
signed for voice and music reproduction and is ideal for
amateur communications, home recording, low cost P.A.
systems, call systems, and all general purpose use.
The durable plastic case of the "Versatex" makes this
microphone especially safe for use with amateur
equipment.
The cartridge unit is mounted in rubber to provide
mechanical isolation from the case, so that the microphone may be handled or carried about without annoying
mechanical noise pickup.
The Model 718A "Versatex" is de-
Versatile Crystal Microphone
SPECIFICATIONS
Connections: The inner or “hot” conductor of the
cable should be connected to the grid of the first tube in
the amplifier across a load resistance of 5 megohms. In-
put resistances as low as 1 megohm may be used if necessary but higher values are recommended because of
better low-frequency response obtained. The shield
should be connected to the amplifier chassis or ground.
The cable may be lengthened if desired; low capacity
shielded microphone cable should be used for this
purpose.
Operation: No polarizing voltage is required for
crystal microphones.
Crystal microphones may be seriously damaged if
accidentally connected to loud speaker or power supply
outlets carrying high voltage. Check your connections
carefully.
Crystal microphones should not be used or kept in
places where the temperature exceeds 125°F. They should
not be exposed to the rays of the sun in very hot weather
for any considerable length of time-or left in closed
automobiles parked in the sun during hot weather, as the
temperature inside the automobile may easily build up to
over 125° and permanently damage the crystal.
When used near a radio transmitter, use the minimum length of cable consistent with placement requirements. Careful grounding of the cable shield is advisable.
Copyright Shure Brothers, Inc., 1947.
27A29 (11 48)
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Height, Overall . . . . . . . . . . . . . . . . . . . . . . . . .
Diameter at Base. . . . . . . . . . . . . . . . . . . . . . . . . . .
Finish
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Maroon
Net Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shipping Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Code Word (7' Cable). . . . . . . . . . . . . . . . . . . . . . . .
718A
5-7/8"
2-19/32"
5/8 lb.
1-1/2 lb.
RUTEX
Voltage Sensitivity: 2.2 millivolts r.m.s. per bar at
the end of a 7-foot cable across 1 to 5 megohms at 400
cycles. This is equivalent to 53 db below 1 volt per bar at
the terminals of the 7-foot cable.
Internal Output Impedance: Equivalent to a
900 micro-microfarad condenser.
Recommended Load Impedance:
Guarantee:
electrical end mechanical defects for a period of one year from
date of shipment from the factory, provided all instructions are
complied with fully. In case of damage, return the microphone to
the factory for repairs. Our guarantee is voided if the microphone
case is opened.
Each microphone is guaranteed to be free from
1 to 5 megohms.
License Notice: Shure patents pending. Licensed under
patents of the Brush Development Company.
Printed in U. S. A.
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