99B-MI Standard Control

The Type 99B Tower Clock Controller is a microprocessor-based master clock that provides completely automatic control of Electric Time minute impulse (MI) clocks & 24 VDC (RP) reverse polarity clock movements. ETL listed to US and Canadian UL standards.

ETL listed

  • 99BMI Controller
  • CTRL-99BMI Wiring Diagram_1
  • 99B Example Installation
Part Number: CTRL-99B-MI.
Category: .

Standard Tower Control

– Provides 24VAC “Minute Impulse” (MI) Control (clock hands index from one minute to the next)
– Drives 24VDC “Reverse Polarity” (RP) clock movements
– Automatically resets clocks after power failures (resets at 6x speed)
– Automatically resets clocks for daylight saving time (if required)
– Precision Quartz Time Based
– Optional GPS for atomic clock accuracy – requires open sky
– Optional CDMA for atomic clock accuracy – when open sky is not available.
– 10 year replaceable battery backup for time base
– For indoor or outdoor use
– Protected to IP65
– ETL listed to UL 863, Seventh Edition & CAN/CSA C22.2 No. 6-M1984

Westminster Chime & Hour Strike available

Additional information available on the documentation tab above.

99B-OPT board available to provide outputs for other clock system and special applications.

If your controller was purchased without the 2007 daylight saving rules – contact us for a software update.




The 99B Tower Clock Control is available with an optional output board which allows control of alternate or legacy clock movements.

Product Matrix

99B-MI Tower Clock Control Options

Part NumberDescriptionBoard Required
CTRL-99BMI-DMDual Motored Synchronous (Electric Time standard since the 1920s) Also Edwards and Auth Dual Motored SystemsCTRL-99B-OPT
CTRL-99BMI-MI-115115VAC Minute ImpulseCTRL-99B-OPT
CTRL-99BMI-NATSplit Phase Capacitor Synchronous 10 x Reset SystemCTRL-99B-OPT
CTRL-99BMI-SC-24VAC24 VAC 58th Minute Hourly/12 Hourly - Output Board not requiredno
CTRL-99BMI-SC-115VAC115 VAC 58th Minute Hourly/12 Hourly - Output Board REQUIREDCTRL-99B-OPT
CTRL-99BMI-STOPStop or wait for system - works with any 115VAC Synchronous Tower Clock SystemCTRL-99B-OPT
CTRL-99BMI-HR-24VACHour Strike no
CTRL-99BMI-PCClock controller for Post Clocks only no
CTRL-RP-EXPExpansion module FOR 24VDC minute impulse movementRP-EXPANSION


How to set the time on a 99B Tower Clock Controller
– Use this tutorial when the time on your Clock controller is incorrect (set:time)


How to set your clock hands using a 99B Tower Clock Controller
– Use this tutorial if the time on your clock controller is correct, but the clock hands read a different time (set:hands)

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