MIL-DTL-62545E
3.3.2 Warning signals. The MSEC shall provide fire warning signals for small and large fires as follows (see 4.6.3).
3.3.2.1 Fire signals. Upon receipt of a signal from the OFSA for a small threshold fire, the MSEC shall energize
the fire warning lamp and an audible fire warning signal without activating the extinguisher drive signals. A large fire
signal occurring while a small fire signal is present shall energize the fire warning lamp, the audible fire warning
signal, and the appropriate extinguisher drive signals. The fire warning circuit shall not lock in the energized position
3.3.2.2 Extinguisher status. The MSEC shall energize four extinguisher status lamps, one for each extinguisher.
These lamps, when energized, shall indicate a continuity break, low extinguisher pressure or that extinguishant flow
has occurred. Continuity loss shall not render the remainder of the system inoperative (see table II and table III)
(see 4.6.3).
3.3.3 BITE. The MSEC shall incorporate BITE capability which conducts to a total electronic check as specified in
3.4.6. A fault signal detected in an OFSA shall cause signals from that unit to be ignored, and the remainder of the
system shall be operative (see 4.6.3).
3.3.4 Configuration. The MSEC shall conform physically and dimensionally to Drawing 12370459 (see 4.6.1 and
4.6.2).
3.3.5 Connector receptacles. The MSEC shall electrically interface with fire extinguishing systems through the
connector receptacles called out on Drawing 12370459 and as specified below (note: MS3474, MS3121 and
MS3114 are inactive for new design). The MSEC internal wiring to the connectors shall provide for its function in,
and interface with, the vehicle and fire extinguishing system as follows (see 4.6.1, 4.6.2, and 4.6.3).
a.
MSEC connector J1: MS3474 W22-21PN, MS3121 W22-21PN, MS3114 W22-21PN or 12343265-2.
b.
MSEC connector J2: MS3474 W22-21SN, MS3121 W22-21SN, MS3114 W22-21SN or 12343265-3.
c.
MSEC connector J3: MS3474 W18-32SN , MS3121 W18-32SN, MS3114 W18-32SN or 12343265-4.
3.3.5.1 Receptacle J1. Receptacle J1 shall communicate with the test and alarm panel, vehicle power, the fire
warnings, and the ventilation fan. It shall be wired for the signal assignments shown in table II (see 4.6.3).
3.3.5.2 Receptacle J2. Receptacle J2 shall communicate with the extinguishers. Receptacle J2 wiring shall be
compatible with the four extinguisher harness variations described on figure 2, and shall provide the signal
3.3.5.3 Receptacle J3. Receptacle J3 shall communicate with the OFSA's. Receptacle J3 wiring shall be
compatible with the four OFSA harness variations described on figure 3, and shall provide the signal assignments
3.3.6 Electrical signals. The MSEC shall receive and transmit logic information and commands in the form of the
four signals described in table I. The MSEC shall withstand signal short circuits of indefinite duration, and shall
perform as specified within all indicated signal value ranges (see 4.6.3).
3.3.7 Extinguishing shots. The MSEC shall function as specified in either one or two shot systems without
3.3.8 Component removal/replacement. Upon removal or replacement of any component, automatic protection
shall be provided within the MSEC to preclude false activation of any of the extinguishers. Removal or replacement
of any OFSA or extinguisher shall not render the remainder of the system inoperative (see 4.6.3).
3.3.9 Reliability. The mean time between failures shall be not less than 100,000 hours (refer to MIL-HDBK-217 for
guidance). A failure shall be defined as any MSEC malfunction which prevents the system from responding as
specified (excluding incidents caused by or exclusively to interconnecting electrical harnesses) (see 4.6.4).
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