Shure 885TT User Guide
HAND-HELD TRANSISTORIZED CONDENSER
DTMF COMMUNICATIONS MICROPHONE
GENERAL
The Shure Model 885TT is a hand-held, amplified, condenser
DTMF communications microphone with an illuminated keypad.
The microphone is ideal for upgrading existing two-way radios for
use with advanced telephone interconnect systems or for new
installations. It is designed for rugged and reliable operation in any
mobile communications application. The 885TT has an omnidirectional pickup pattern and provides extremely clear transmission,
even in noisy environments. In addition to its clear, crisp, natural
voice response, the 885TT has extremely low sensitivity to hum
pickup and low susceptibility to radio frequency interference.
For installations where transmitter input gain requires sensitivity
modification, the 885TT has convenient, externally accessible
screwdriver controls for independent adjustment of both microphone and DTMF levels. This eliminates the problem of fixed audio
levels and the necessity for disassembling the microphone for adjustments. Restricting control access also prevents accidental
changes common to external controls.
The 885TT is designed for use with most currently available mobile two-way radio transceivers. For installation convenience, all
microphone and signalling functions, including keypad illumination,
are powered directly from the microphone input circuit of most
transmitters, minimizing the need for equipment modification. The
microphone is compatible with a choice of five-conductor, prewired, coil-cord MODULINK cables (sold separately), each of
which has a telephone-type modular plug on the microphone end,
and a choice of popular transmitter input connectors on the other.
Model 885TT User Guide
One cable model is supplied without a connector on the transceiver
end so that the user or installer can attach the desired connector.
The cables are instantly changed or replaced without soldering.
The 885TT features attractive, contemporary styling, designed
to blend with most radio designs and vehicle interiors. The microphone is ergonomically designed; it fits naturally and comfortably in
the hand and is not affected by heat or humidity. The rugged
ARMO-DUR
vents, salt spray, sun, rust and corrosion. It is outstanding in its ability to withstand mechanical shocks and vibration. The Million-Cycle
leaf-type switch is a double-pole, single-throw type, de-
Plus
signed to resist the effects of severe operating conditions and
constant usage. It has nickel-silver blades, and its contacts are palladium-alloyed for reliable, oxidation-free operation.
The 885TT’s keypad is made of tough silicone rubber, with durable printed characters that will last the life of the microphone. The
keypad is backlit by red LEDs, easily visible during night operation
and minimizing eye readjustment for night vision.
The 885TT is supplied with a small screwdriver for adjusting the
microphone amplifier gain and DTMF level, and for releasing the
modular-plug microphone cable from the microphone. Mounting
brackets for affixing to radio equipment or other surfaces are available in quantities of three as Shure RK6MB.
Features
•Top-Talk Sound Channels for clear voice input, easy handling
•Built-in transistor amplifier (powered by carbon-microphone-
type circuit)
•Frequency response from 200 to 4,000 Hz, tailored for voice
communications
•Illuminated keypad with positive tactile feel and audible con-
firmation tones
•Auto push-to-talk (APTT) automatically keys transmitter when
keypad is depressed
•Convenient external microphone gain adjustment accommo-
dates most input circuits
•Simple, easy-to-use continuous-tone dialing
•Externally accessible DTMF level adjustment, independent of
microphone gain setting
•Modular-plug coil-cord—easily attached and removed. Available
with plugs to fit most popular radio sets
•Low sensitivity to hum pickup
case is immune to oil, grease, most fumes and sol-
NOTICE:
This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) this device may not
cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.
2000, Shure Incorporated
27B3048 (TL)
1
Printed in U.S.A.
•Low susceptibility to radio frequency interference
•Rugged Million-Cycle Plus leaf-type switch stands up under se-
vere environments and constant use
•High-impact ARMO-DUR case—stronger and lighter than die-
cast metal, comfortable to the touch in hot or cold weather
•Rugged and dependable under all operating conditions
•Sturdy, convenient mounting button for attaching to equipment
or nearby surface using optional mounting bracket
•Hang-up button connection available for microphone hang-up
sensing (Mounting bracket must be grounded.)
SPECIFICATIONS
(Test conditions unless otherwise specified: audio output measured between pin 2 and ground; PTT switch depressed; no hangup button connection; mic and DTMF level trimmers full clockwise;
dc DMM 10 M or greater input impedance; ac DMM 1 M or
greater input impedance. Test circuit as shown in Figure 3B.)
Type
Electret condenser (with transistor preamplifier, DTMF signaling
circuitry, illuminated keypad)
Frequency Response
200 to 5,000 Hz (see Figure 1)
+10
PTT Switch Assembly
Mechanical: Double pole, single-throw, leaf-type, normally
open
Electronic: Open NPN transistor collector to ground; positive
polarity only; maximum on-state current 100 mA to
produce 0.8 V or less; maximum off-state voltage
40 V.
Cable (optional choice)
Detachable, 1.4 m (48 in.), 5-conductor (1 shielded), vinyl-rubber-jacketed coil cord with modular plug on microphone end (see
Cordset Table for available installed equipment plugs)
Construction
Case: Black textured high-impact ARMO-DUR. . . . . . . . . . . . .
Switch Button: Black ARMO-DUR. . . . . . . . . . . . . . . . . . . . . . .
Keypad: Molded silicone rubber. . . . . . . . . . . . . . . . . . . . . . . . . .
Dimensions
See Figure 2
44.4 mm
(1-3/4 IN.)
40.4 mm
(1-19/32 IN.)
70 mm
(2-3/4 IN.)
64 mm
(2-1/2 IN.)
101 mm
(3-31/32 IN.)
0
dB
–10
20 200001000 1000050 100
98765432
Hz
98765432
TYPICAL FREQUENCY RESPONSE
FIGURE 1
Polar Pattern
Omnidirectional
Output Level (at 1,000 Hz, 1 cm)
–26 dB/Pa (0 dB = 1 V/Pascal)
DC Supply Current
2.3 mA
Magnetic Hum Sensitivity
–94 dBV maximum in 1 Oe 60 Hz field (mic level control full coun-
terclockwise)
DTMF Output Level
1.1 V peak-to-peak
Audio Polarity
Positive sound pressure produces positive voltage at pins 2 and
6 of modular connector with respect to ground
Environmental Conditions
Operating Temperature: –30
Storage Temperature: –40
° to 60° C (–22° to 140°F). . . . .
° to 74° C (–40° to 165° F). . . . . . .
Relative Humidity: 0 to 95% (non-condensing). . . . . . . . . . . . .
Microphone Connector
6-conductor modular telephone type
OVERALL DIMENSIONS
FIGURE 2
Net Weight
149 grams (5.2 oz)
CONNECTIONS
The 885TT is designed to operate with two-way radio sets with
input circuits similar to those in Figure 3. When wiring ALM-1 cables
with connectors for radios not listed in the table, modular connector
pin 2 is to be used for the dc bias resistor on the input (see
section).
tions
560
TO
PIN
2
1 K 560
Modifica-
TO
PIN
2
8 – 13 VDC
(A) (B)
MICROPHONE INPUT CIRCUITS
FIGURE 3
2
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