This set of videos, via SonicVoltage, takes an in-depth look at the Orthogonal Devices ER-101 & ER-102

The Orthogonal Devices ER-101 is a Eurorack Modular Four Track Gate and CV Sequencer, with 1 Gate and 2 CV channels per Track.

The ER-102 is the Sequencer Controller expander module, which augments overall sequencing and modulation capabilities and also adds CV/Gate Recording.

Details on the modules are available at the OD site.