1. Maximum Power Dissipation (Power - Max): DTC144 is rated for 200mW, while RN1113 is rated for 100mW. Implication: The RN1113's power handling capability is only half that of the DTC144. If the original circuit design operates the transistor near 100mW, a direct substitution will cause the RN1113 to overheat, significantly increasing long-term reliability risks. During replacement, the actual power dissipation under operating conditions must be recalculated or measured to ensure an adequate safety margin. 2. DC Current Gain Test Condition (DC Current Gain @ Ic, Vce): DTC144 is specified at 5mA, 10V; RN1113 is specified at 1mA, 5V. Implication: While both have a minimum hFE of 120, the differing test conditions suggest potential variations in their gain-current characteristics. At the same actual operating current (e.g., 5mA), the actual gain values of the two devices may differ. This can affect circuit drive current, switching speed, or amplification linearity. 3. Saturation Voltage Test Condition (Vce(sat) @ Ib, Ic): DTC144 is 250mV @ 1mA, 10mA; RN1113 is 300mV @ 250µA, 5mA. Implication: This parameter directly determines conduction loss in the switching state. The RN1113's test condition (with both lower base and collector currents) is less stringent than the DTC144's, yet its specified maximum saturation voltage (300mV) is higher. This indicates that at the same 10mA load current, the RN1113's actual Vce(sat) is likely significantly higher than the DTC144's, leading to greater conduction voltage drop and power dissipation. 4. Transition Frequency (Frequency - Transition): RN1113 is specified at 250MHz, while this parameter is not specified for the DTC144. Implication: Although pre-biased transistors are often used for low-frequency switching, this parameter reflects the device's high-frequency capability. The RN1113's specification indicates a defined capability for high-speed switching, potentially offering better performance and predictability in circuits involving fast switching or requiring controlled edge rates. The absence of this specification for the DTC144 suggests its high-frequency performance may be weaker or is not a guaranteed focus.