两岸政治互信 enhance mutual political trust between the two sides ; cross-Straits political trust

两个互信机制 the two "Confidence-Building Mechanisms"

两信道跟踪接收机 Dual Channel Tracking Receiver

两种信号系统学说 theory of two signal systems

两封推荐信 Two Letters of Recommendation ; Two reference letters ; Reference / Letter of Recommendation

两种信号系统 two signaling system

两相调制器信号 biphase modulator signal

两封信 two letters

推荐信两份 Reference Letters