Replaces obsolete or un-serviceable stepper units in older elevators

Many older elevator systems use vertical selectors to determine car and landing position. These systems are complex and expensive to maintain—if parts can even be sourced. Electrodyn’s Stepper Unit Replacement (Model 722) is a solid upgrade that solves this problem by eliminating the need for vertical selectors. The board sends an electronic pulse to the machine room to indicate car/landing position. This economical retrofit is compatible with all control systems and is also available in a lift-off door cabinet.

Model 722 employs analogue relays that are far superior to chip-set solutions in terms of price and maintenance. Step dampening prevents signal flutter, and rugged onboard 5-amp outputs ensure unit survival in higher voltage environments.


When installing the Stepper Unit, interface relays are matched to the control voltage and isolated from logic circuits. The interface is accomplished with a series of parallel connections, with one connection per position in each bank. Usually found at the main line input, an independent power source of 120/220 VAC is required. Both the bank inputs and power supply are fused. During initial power-up, floor position is established at a terminal. During a power-loss event, car position is retained in the Stepper Unit's onboard memory. Model 722 recognizes the condition in which the car is behind the stepper when the stepper’s first position is reached, resulting in the car being sent to the top terminal for reset. Resetting is provided at both terminal landings.

Complete Package

The Stepper Unit comes complete with revised wiring diagrams and “pony sheets” for a step by step guide through the installation process. We also provide free technical support. 


• Battery backup provides memory
• Incorporates relay logic for increased reliability
• Top and bottom reset
• 4 pole relays with neon indicator displays
• 5 amp output contacts ensure durability and compatibility
• Provides 2 banks and up to 18 positions
• Installation time: 3.5 hours