TM 1–1520–238–T–3
1–7
9. Scalar conversions are used to interpret analog to digital and digital to analog signals. Some examples of
these signals are degrees, meters, kilometers per hour, and signal strength. The important requirements to note on
scalar conversions are the sixth digit (sign digit) and whether an increase or decrease is occurring on the HOD
while the operation is being performed. A 1 displayed in the sixth digit indicates a negative number or response, a
0 indicates a positive number or response. For example, increasing ORT brightness should show an increasing
reading on the HOD, while decreasing brightness should show a decreasing reading (toward zero) on the HOD.
Scalar conversions are used when (SCALAR) appears after MEMORY DATA BIT(S) in the respective paragraph.
EXAMPLE:
22–2 SIGNAL NAME: ENG 2 TORQUE
MEMORY LOCATION: 000120
MEMORY DATA BIT(S): 4–19 (SCALAR)
CONDITION: Monitor HOD while turning up engines; memory location response digits
should increase and display will limit at 120.
SIGNAL FUNCTION: Monitors engine 2 torque.
REMARKS: From engine 2 torque sensor to engine 2 ECU through DASEC to FCC.
PASS: If CONDITION is met, go to Chapter 14, paragraph 14–135.
FAIL: Location of fault: engine 2 torque sensor, wiring from engine 2 torque sensor to
ECU, ECU, wiring from ECU to DASEC, DASEC. Troubleshoot wiring to isolate
fault (TM 1–1520–238–T–4).
10. Specialized system conversions are presented in the applicable system chapter.
1–10 CONDITION.
CONDITION is a requirement prerequisite or selection which specifies information that enables interpretation of
digits displayed on the HOD. CONDITION allows comparison of known or expected system configurations, and
physical aircraft conditions, with the digits displayed on the HOD. Included under CONDITION are: switch settings,
heading, gun, rocket, missile and pylon responses, and reference to ASCII code conversions. (None) indicates that
there are no special conditions required and that activities are controlled by the MOC that is in progress.
EXAMPLE:
CONDITION: If fourth digit displayed on HOD is 0 = STBY.
If fourth digit displayed on HOD is 1 = RANGE.
If fourth digit displayed on HOD is 2 = FD/LS.
If fourth digit displayed on HOD is 3 = (NOT USED).
If fourth digit displayed on HOD is 4 = TGT.
If fourth digit displayed on HOD is 5 = CODE.
If fourth digit displayed on HOD is 6 = SP1.
If fourth digit displayed on HOD is 7 = OFF.
1–11 SIGNAL FUNCTION.
SIGNAL FUNCTION indicates the purpose or relationship of a SIGNAL NAME to a system or systems. Some of
these relationships are monitoring, indicating, enabling, commanding, selecting and initiating a system function.
EXAMPLE:
SIGNAL FUNCTION: Monitors position of DEK rotary switch.
