268 MAINTENANCE AND LUBRICATION Note: The tachometer output and speedometer output are 50% duty cycle, Transistor-Transistor Logic (TTL) compatible, square wave signals that are calibrated to provide a standard pulse rate of 12 pulses per engine revolution for the tachometer output and 30,000 pulses per mile for the speedometer output. TTL compatibility of these outputs may be affected by other devices connected to these outputs. Tachometer (RPM) Output This terminal is to be used for devices requiring information for engine speed signals. (See the Warning and Note above.) Speedometer (MPH) Output This terminal is to be used for devices requiring information for vehicle speed signals. (See the Warning and Note above.) SAE/ATA J1708 Posts (Serial Links A and B) This is a serial communication interface. It conforms to the SAE/ATA J1708 Recommended Practice for Serial Data Communications Between Microcomputer Systems in Heavy-Duty Vehicle Applications. (See the Warning above.)
CAUTION The electrical systems on all MACK chassis include a circuit breaker located in the ground circuit. Any additional electrical components that may be added MUST not be connected directly to the battery or negative connection of the starter. Doing so may defeat the protection provided by this circuit breaker. Components may be ground connected to other locations, such as frame or engine grounding points.
This MACK chassis is ready for convenient installation of electrical accessories. Use only the designated CB jacks on the dashboard, or battery post (12 volts), ignition, ground post, buffered tachometer (RPM) output, and buffered speedometer (MPH) output connections available on the electrical equipment panel. Each connection point is described below. Battery Post (BATT)
