Assume that each character code consists of 8 bits and the asynchronous serial…

Concept: On an asynchronous serial line, data moves one character at a time, and every character is wrapped in a fixed frame of overhead bits. The frame length is the sum of the data bits plus the framing bits (start, stop, and parity). In binary signalling one baud equals one bit-time per second, so the line carries (baud rate) bit-times every second. The achievable character rate is therefore the bit rate divided by the number of bit-times consumed by one whole frame, and only frames that fit completely within one second are counted.

Application:

1. Size one frame: 8 data bits + 1 start bit + 2 stop bits + 0 parity = 11 bit-times per character.

2. Convert the line rate: binary signalling means 2400 baud = 2400 bit-times per second.

3. Divide bit rate by frame size: 2400 / 11 = 218.18 characters per second.

4. Keep only whole characters: a partial frame at the end is not a complete character, so the count is the integer part, 218.

Cross-check: 218 frames use 218 × 11 = 2398 bit-times, leaving only 2 of the 2400 bit-times — not enough for a 12th-of-its-kind full 11-bit frame, which confirms 218 is the largest count of complete characters. Note the common trap: forgetting that one baud is one bit-time (not one character) inflates the frame, and double-counting the data bits (treating the frame as 22 bit-times) would wrongly give 2400 / 22 = 109.