Electro-Voice 625HS Handset Microphone User Manual

May 15, 2024

Voice 625HS Handset Microphone
User Manual

625HS Handset Microphone

SPECIFICATIONS Current Drain: 22 mA at 14 volts
Polar Pattern:
Bi-directional pressure gradient (drfferential close-talkirg) Rated Supply

6-20 V d.c.
Output level:| Dimensions:
-48 dB| 211.1 mm (8.31 in.) long
60.3 mm (2.37 in.) wide
66.7 mm (2.62 in.) hig
Impedance,| Net Weight:
Microphone: 150 ohms| 397 g (14.0 oz)
Receiver.| Cable:
150 ohms| 5-conouctor coiled cord, 5′ extendedConnector:
None supplied
Electro-Vo,ce Acoustal1o| Switch:
Press to talk (non-shorting type)and relay  switch
Finish:| Temperature Range:
Blacl<| -40° c (-40° F) to +70° C (+158° F)
Amplifier Gain:| FAA Type Certificate:
0-35 dB ad1ustable| TSO C-57, csa


The Electro-Voice Model 625HS is a noise cancelling handset microphone, designed for high articulation speech transmission under 5high ambient noise conditions. The model 625H$ is the result of continuous study of the needs of the communication industry and it uniquely meets the specialized requirements of airline, two-way radio and industrial applications. This handset employs a transistorized pressure gradient microphone utilizing two sound entrances for reduction of interfering ambient noise. Stated simply, if sound pressure and phase are reasonably identical at both sound entrances, cancellation occurs. If, however, the sound originates in close proximity to one sound entrance (i.e. % or V2 inch) and more distant to the other sound entrance, then a pressure and phase diffentiat will exist and litte cancellation will occur. The 625HS is unexcelled at discriminating between near and distant sounds for maximum ambient norse rejection. The compact transistor amplifier is specially stabilized and will operate uniformly from 70°C (+ 158F) down to — 40°C (-—40°F). Output of the transistor amplifier is designed to wire directly into iNputs designed for carbon microphones. The 62SHS provides extremely reliable, crisp, clear speech reproduction with high sensitivity and low distortion .Electro-Voice 625HS Handset Microphone 1


  1. Special Tools: None

  2. Disassembly: (See Figure 4)
    a. Remove microphone cap, lift out housing.
    b Note lead hookup arrangement on terminal board.
    c Rmove leads from terminal board only if head needs replacing.

  3. Inspection:
    a Examine unit for damage or dried-out wiring or sleeving. Check ail terminal connections for good contacts.
    b. Check cable for signs of damage such as cuts or cracks.

  4.  Repair and Replacement:
    a. Replace any part which is damaged.
    b. Check resistance across the head with an ohmmeter. It should be about 1500 ohms + to —and 150 k ohms — to +. Remove head/amp S/A if improper readings are observed.

  5. Reassembly:
    a. Reassembly is the reverse of disassembly.

  6. Test Procedure: (See Figure 3)

  7. Check of Switch Operation: Check the operation of the switch as follows:
    a. With the switch released, check the resistance between the biue and green leads. It should be infinite.
    b. Check the resistance between the white and black leads. It should be as 4b.
    c. Depress switch and check resistance between blue and green leads. It should be zero.
    d. Check resistance between red and green leads. It should read approximately 30 ohms.
    e. Depress switch and check resistance between white and black leads. It should be approximately 1500 ohms. See Note 4b.

  8. Check of Microphone Output: The best procedure for testing the microphone is to compare its output with one known to be operating properly, using the test set-up as shown in Figure 3. Check the output voltage as follows:
    a. Hold the test microphone about Ye inch from the mouth and talk at normal speech level with micro- phone switch depressed. An output of about .030 volt should be obtained across the 150-ohm resistor.
    b. Adjust gain using adjust if necessary.
    Electro-Voice 625HS Handset Microphone - fig

WARRANTY (Limited)
Electro-Voice Aircraft Microphones are guaralteed for a period of eighteen months from date of original purchase against malfunction due to defects in workmanship  and materials. If such malfunction occurs, microphone will be repaired or replaced (at our option) without charge for materials or labor if delivered prepaid to the proper Electro-Voice service facility. Unit will be returned prepaid. Warranty does not extend to finish, appearance items, cables, cable connectors, switches or malfunction due to abuse or operation under other than specified conditions, nor does it extend to incidental or consequential damages. Some states do not allow the exclusion or limitation of incidental or consequential damages, so the above exclusion may not apply to you. Repair by other than Electro-Voice or its authorized service agencies will void this guarantee. A ist of authorized service agencies is available from Electro-Voice, Inc., 600 Cecil Street, Buchanan, MI 49107 (AC/616-695-6831): Electro-Voice, Inc., 3810 148th Avenue, N.E., Redmond, WA 98052 (AC/206-881-9555); and/or Electro-Voice West, 8234 Doe Avenue. Visalia, CA 93291 (AC/209-651-7777). This warranty gives you specific legal rights, and you may also have other rights which vary from state to state.
Service and repair address for this product: Electro-Voice, inc.. 600 Cecil Street. Buchanan, Michigan 49107. Specifications subject to change without notice.

ELECTRO-VOICE, INC., 600 Cecil Street, Buchanan, Michigan 49107
@Electro-Vorce. inc 1988 M Litho IN USA Part Number $3779—622
MARK IV company,


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