Shure 885TT User Guide

Model 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.

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 case is immune to oil, grease, most fumes and solvents, salt spray, sun, rust and corrosion. It is outstanding in its ability to withstand mechanical shocks and vibration. The Million-Cycle Plus leaf-type switch is a double-pole, single-throw type, designed to resist the effects of severe operating conditions and constant usage. It has nickel-silver blades, and its contacts are pal- ladium-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 confirmation tones

•Auto push-to-talk (APTT) automatically keys transmitter when keypad is depressed

•Convenient external microphone gain adjustment accommodates most input circuits

•Simple, easy-to-use continuous-tone dialing

•Externally accessible DTMF level adjustment, independent of microphone gain setting

•Modular-plug coil-cordÐeasily attached and removed. A vailable with plugs to fit most popular radio sets

•Low sensitivity to hum pickup

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	1	Printed in U.S.A.
	27B3048 (TL)

•Low susceptibility to radio frequency interference

•Rugged Million-Cycle Plus leaf-type switch stands up under severe environments and constant use

•High-impact ARMO-DUR caseÐstronger and lighter than diecast 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)

dB	+10
	0
	±10
					2			3		4 5 6 789								2		3		4 5 6 789
	20		50		100					1000												10000								20000

Hz

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 counterclockwise)

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° to 60° C (±22° to 140° F) Storage Temperature: . . . . . . . ±40° to 74° C (±40° to 165° F) Relative Humidity: . . . . . . . . . . . . . 0 to 95% (non-condensing)

Microphone Connector

6-conductor modular telephone type

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-rub- ber-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	70 mm
	(1-3/4 IN.)
		(2-3/4 IN.)
	40.4 mm
		64 mm
	(1-19/32 IN.)	(2-1/2 IN.)

101 mm

(3-31/32 IN.)

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 Modifications section).

560	TO	1 K	560	TO
	PIN			PIN
	2			2

8 ± 13 VDC

(A)

(B)

MICROPHONE INPUT CIRCUITS

FIGURE 3

2