(chiefly US, typography) The hash or square symbol #, used mainly in telephony and computing.
The pad 1 provides keys for numerals 0 to 9, while the sextile or asterisk (*) key is decoded to provide a decimal point and the octothorp ( # ) key generates a command to send the contents of the memory unto the telephone line through a send circuit 7, a coupling circuit 8 and the hybrid network 2.