The series ЭР1, ЭР2 and ЭР9 (ER1, ER2 and ER9) denote electric multiple units for suburban traffic, of which over 10,000 cars were manufactured and which came to a total of almost 40 years of production. The design was based on a type of three-car multiple units for 3,000 volts direct current, which were built from 1949. In order to increase the capacity to meet the requirements, the concept of two-car train parts was developed. These each consisted of a control car and a motor car or a trailer and a motor car, so that in all possible combinations every second car always had a pantograph and power on all four axles. These had the center buffer couplers common in the Soviet Union, so they could be coupled and uncoupled quickly. The trains were mainly used as ten-car trains, but four-, six- and eight-car combinations were also possible.

From 1957, initially the vehicles of the ЭР1 type were built, the doors of which were only suitable for the high platforms of the well-developed urban suburban railways. The passenger compartment was designed as one large room and had six seats per row with an aisle. The ЭР2 introduced more modern technical equipment with initially the same optics and the entrance areas were now equally suitable for high and low platforms. About 9,200 cars of this model were built in Riga and Tver from 1962 to 1984 and distributed throughout the Soviet Union. Later examples received redesigned driver's cabs with angular cladding. The power selector of the ЭР1 and ЭР2 work as usual with DC railcars with series-parallel circuits and resistors. The ЭР9 was the variant for 25 kV alternating current, which was otherwise similar in structure to the ЭР2 and was controlled by a tap changer.

The production of these vehicles ended in 1995 after more than 4,000 cars of the ЭР9 series. In 2001 and 2003, a ten-car train each followed in Kyiv, which were assembled from existing assemblies. During the construction period, the interior furnishings in particular were modernized. For example, the wooden benches were replaced with upholstered seats and the materials and lighting in the interior were updated. New technologies were tested with individual vehicles, for example in the area of control electronics. Vehicles with batteries were also built, which could also be used on non-electrified sections. Existing vehicles were also modernized over time and some were fitted with completely redesigned car bodies. The oldest vehicles, if they were in the appropriate condition, were taken out of service in the 1980s, and some were converted into two-car service vehicles. By 2010, the majority had already been retired, but some were still in use in Latvia, for example.