The Model 550 Vibration Transmitter/Switch provides low cost, reliable vibration protection for rotating machinery operating within the range of 120- 60,000 rpm. The switch's vibration sensor, mounted perpendicular to the unit's base, responds to the velocity (in/sec) signal and effects automatic shutdown or alarm when preset limits are exceeded. The unit may be mounted with the sensitive axis in any plane (horizontal, vertical, or axial), even in an inverted position. Two limit set points are provided. One is set for the maximum allowable vibration (in/sec), while the other is set for a percentage of that setting, which trips the alarm relay when that percentage is reached. A built-in, adjustable time delay prevents triggering due to transient vibrations. The switch can be wired for automatic reset when vibration falls below setpoint, or it can be wired for latch and remote reset. The unit has a 4-20 mA output that may be used with a panel meter or data logger, permitting analysis of vibration trends. Once the switch has been installed and the limits set, it requires no attention. The Model 550 is enclosed in heavy, water-tight cast-aluminum housing. Explosionproof housings are available.