Woodland Hills, California-based American Mobile Systems Inc signed definitive agreement for the previously announced sale of a majority equity interest in itself to Nextel Communications Inc for $7 a share: Nextel will buy at least a majority and up to about 61% of the fully diluted number of common shares and will pay at least $50m, at least $20m of that in cash, and the 61% includes about 714,000 shares sold to Nextel in April for $5m cash.