The DS3231SN is a low-cost, extremely accurate I²C real-time clock (RTC) with an integrated temperature-compensated crystal oscillator (TCXO) and crystal. The device incorporates a battery input, and maintains accurate timekeeping.
These epitaxial planar transistors are mounted in the TO-126 plastic package. The PNP types are the BD136 and BD140, and the complementary NPN types are the BD135 and BD139.
The DS1302Z is a trickle-charge timekeeping chip contains a real-time clock/calendar and 31 bytes of static RAM. It communicates with a microprocessor via a simple serial interface IC SOP-8 Pins Package.