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127 This configuration also shows how to connect a reset switch. A reset switch is sometimes useful, particularly during debugging, to get the ZX to start running its program from the beginning. If the reset is also connected to other external circuitry, you may wish to isolate the ZX from the remaining circuitry so that the on-board resets that occur during downloading are not also applied to the external devices. A simple isolation circuit employing a small signal diode is shown below. You can also implement an isolation circuit using a discrete transistor or an open-collector gate. Reset Signal Isolation B.2 Pin Configuration The ZX-24 series devices have 24 male pins, numbered 1 through 24 in a standard DIP configuration. Additionally, there are 10 other connections that may be made to the ZX-24 series circuit board for expansion and other special purposes. In the diagram below, the male pins are represented by filled circles while the open circles represent solderable connections. The filled square indicates pin 1. The remaining rectangles on the diagram are stylized representations of some of the components on the board and are shown for orientation purposes only. Pins 1 to 24 are referred to as the standard pins while the remaining connections are referred to as the expansion pins. ZX-24 Series Pin Configuration B.2.1 Standard Pins The table below summarizes the functions of the standard ZX-24 series pins. A detailed description of each pin is given following the table. Note that several of the external pins connect to more than one pin