In new designs, no engineer would spec an Rki 057. A modern solid-state latch (e.g., a D-type flip-flop or an EEPROM) is smaller, cheaper, and has no moving parts. However, for retrofitting or repair, the Rki 057 retains unique advantages:

| Feature | Rki 057 (Electromechanical) | Modern Solid-State Latch | | :--- | :--- | :--- | | Isolation | True galvanic isolation (kV range). | Requires optocouplers for high isolation. | | Contact Resistance | Milliohms when closed. | Several ohms when on. | | Surge Immunity | Immune to static and inductive kickback (within reason). | Sensitive to ESD and voltage spikes. | | Visual State | Often has a mechanical flag or audible click. | Requires an LED or software readout. | | Vibration Tolerance | Moderate (susceptible to shock). | Excellent. |

For restorers of vintage Prophet 5 synthesizers, Telefunken tape decks, or 1960s mainframes, the Rki 057 is irreplaceable—not just for historical accuracy, but because it actually performs better in legacy circuit environments that lack proper transient suppression.

Because many Rki 057 units were used in low-current signal applications (e.g., 5V logic), the contacts can develop a layer of oxide or sulfide, leading to intermittent connection or increased resistance.

Solution: Do not use sandpaper. This removes the precious metal plating. Instead, use a paper strip soaked in isopropyl alcohol, or a specialized contact burnishing tool.

Despite its legendary durability, the Rki 057 is not immortal, especially given that most units in circulation are 40+ years old. Here are the common issues encountered by restorers: