Outerwall, the Bellevue company formerly known as Coinstar, said Tuesday it has agreed to buy ecoATM, the creator of an automated self-serve kiosk system used to buy used mobile phones, tablets and MP3 players for cash.

Outerwall already operates a variety of automated retail business including Coinstar coin-counting machines and Redbox DVD rental machines.

The company valued the deal at about $350 million in cash including the payoff of certain debt and transaction costs. Outerwall also said that because it holds a 23 percent stake in ecoATM, consideration for that stake will be deducted from the actual cash paid. When the deal closes, Outerwall will own all of ecoATM.

The kiosks that ecoATM created use electronic diagnostics to evaluate the items and connect consumers with worldwide secondary markets for the best possible pricing.

Outerwall said ecoATM capitalizes on the growing U.S. mobile-device market. It estimated that only 20 percent of used mobile phones are currently collected, with more than 50 percent being discarded or stored, representing a significant opportunity for growth.

Meanwhile, demand for used mobile phones continues to accelerate, mainly as a result of growth in emerging markets.

Outerwall said it expects ecoATM to boost its profits starting in 2014. The deal is expected to close in the third quarter.

The ecoATM business will remain based in San Diego, Calif.

Also Tuesday, Outerwall shares started trading under their new ticker “OUTR.” The ticker stemmed from the company’s name change, which was shareholders approved last week. The stock previously traded under the ticker “CSTR.”

Outerwall CEO J. Scott Di Valerio rang the opening bell at the Nasdaq stock market to celebrate the first day of trading under the new ticker. The stock closed up 99 cents, or 1.6 percent, at $61.29. The shares have traded in a 52-week range of $40.50 to $71.82.