This SAE Aerospace Standard (AS) covers tachometer instruments (RPM indicator, 0-110 percent RPM and 0-120 percent RPM indicators and generator) for remote indication of engine speed.
SAE AS432B-2008 history
2008SAE AS432B-2008 TACHOMETER INSTRUMENTS (Indicator and Generator)
1996SAE AS432B-1996 TACHOMETER INSTRUMENTS (Indicator and Generator)
1963SAE AS432A-1963 TACHOMETER INSTRUMENTS (INDICATOR AND GENERATOR)