BC557 is a PNP transistor hence the collector and emitter will be closed (Forward biased) when the base pin is held at ground and will be opened (Reverse biased) when a signal is provided to base pin. This is where a PNP transistor differs from a NPN transistor, a Logic state (blue colour) is used to toggle between Ground and Signal Voltage (Emitter-Base Voltage VBE) .
Package Type: TO-92
Transistor Type: PNP
Max Collector Current(IC): -100mA
Max Collector-Emitter Voltage (VCE): -45V
Max Collector-Base Voltage (VCB): -50V
Max Emitter-Base Voltage (VBE): -5V
Max Collector Dissipation (Pc): 500 Milliwatt
Max Transition Frequency (fT): 100 MHz
Minimum & Maximum DC Current Gain (hFE): 125 to 800
Max Storage & Operating temperature Should be: -65 to +150Centigrade