MIL-PRF-49078A(CR)
h. Output impedance of the earphone at 1000 Hz of 1000 ohms + 10 %.
3.2.2 Control switch (push to talk). Shall allow operator positive-controlled transmissions. This
shall be verified by the microphone circuit closing before the control circuit closes and the control
circuit opening before the microphone circuit opens.
3.2.3 Ease of operation. Shall allow easy holding and activation with one hand utilizing gloves.
The physical force necessary to actuate the transmit mechanism with one hand shall be between
two and four pounds.
3.2.4 Accessibility and retention. Provide means integral to the handset for personal retention
compatible with operator clothing or other (for instance, pockets, belts, etc.) when the handset is
not in use and ready operator accessibility under normal field operations. The retention device
will ensure fastening to operator clothing by being able to withstand a minimum of 12 pounds of
pressure perpendicular to the longitudinal axis without distortion or loss of retention.
3.2.5 Camouflage. The handset shall be black and not reflective. Reflectance shall not exceed ten
percent at different points on the handset surface using a 60 degree glossmeter.
3.2.6 Identification. Prominently display the handset designator, H-250( )/U, on the outer
surface of the handset in permanent, easily visible, straight simple letters and numbers.
3.2.7 Pin Out. The five pin audio connector, U-229A/U, shall be wired accordingly: D-A
Microphone Circuit, C-A Control Circuit, B-A Audio Input Circuit (Earphone), E Open. Refer to
schematic diagram, Figure 2, provided for internal connection guidance.
3.3 Interface requirements. Each handset shall accommodate the following inputs and interfaces.
3.3.1 Handset/transceiver interconnection. The handset shall be terminated with a U-229A/U
connector and mate with either the U-183/U or U-228/U. (Refer to MIL-C-55116/1 for
dimensions only.)
3.3.2 Operations range. Means for connecting the handset to the transceiver shall be retractile
for safety, measuring no longer than fifteen inches retracted and between six and eight feet in
length fully extended. Use Whitney Blake part number 9-5133-32-92 or equal.
3.3.3 Weight. Weigh no more than two pounds, including any physical means of connection to
the transceiver.
3.3.4 Outline dimensions. Refer to Figure 3. The mechanism for attaching the handset to
clothing or other shall be 2.0+.125 inches in length, 0.503 inch maximum in width and 0.031 inch
maximum spacing from the body of the handset.
3.3.5 Earphone thickness. Earphone thickness shall be a maximum of 0.9 inch. at its thickest part
(see figure 3).
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