0
The DB25 connector was designed by Bell Labs to connect a variety of different modems to terminals. At the time the phone company owned all the wires and everything that connected directly to them, thus they owned your phone and any modem you used with a terminal to connect to tymeshare services. The 25 pin cable that connected the DB25 (DCE) on the modem to the DB25 (DTE) on your terminal was owned by you. Thus the DB25 connector on the modem was the property line that allowed you access to use the phone line for digital data via a phone company owned modem. This was eventually standardized as RS-232.
It was your responsibility to set the DIP switches on your terminal to be compatible with the phone company owned modem that they supplied. The most common early modem was the 300 BAUD asynchronous full duplex modem but the 1200 BAUD asynchronous half duplex modem was also available. Both used the same DB25 but the half duplex modem used some additional wires for handshake to switch line direction, under control of the modem. There were also higher speed synchronous modems that generated clocks for your terminal, the clocks used more additional wires. All 25 pins are preassigned some modem related function in RS-232.
After the law was changed to allow third party devices to connect directly to the phone line, there was much innovation and much faster modems (most asynchronous full duplex). The DB25 was still usually used to connect to these modems but it no longer defined a property line, it was just the connectors on the cable. Eventually modem companies started making cards that plugged into desktop computers and the phone line plugged into the card, making the DB25 obsolete.
The DB25 and the RS-232 standard have been much misused, to connect all sorts of devices that are not modems to computers... who is the "modem" and who is the "terminal". These devices often use handshake lines in ways that are illegal by RS-232, or use lines that RS-232 reserves for special but rarely used modem functions.
Wiki User
∙ 11y ago
Add your answer:
Earn +20 pts
What is the function of dust?
Dust has no function; it simply exists.
Colonial legislators saw their primary function as?
Colonial legislators saw their primary function as?
What was most likely the purpose of the Altamira cave paintings?
To serve a ritual function.
What was the function of the senate?
senate is the upper house and its function is to make law,rules and ordinaces in the parliament
What colour were the function keys on a BBC microcomputer?
The function keys on the BBC Microcomputer were coloured red.
What is the purpose a DB25?
hey
What is female DB25 connector?
a parallel port
What type of a port is a female DB25 connector?
Parallel
The DB25 connector on the rear of the PC is used normally used to connect what?
The DB25 connector on the rear of a PC is used (if it has pins) to connect a printer or (if it has sockets) to connect a modem.
Which two SCSI connectors might be used with narrow SCSI?
DB25 SCSI connector50 pin SCSI connector
Does the USB to serial cable (DB9/DB25) also come in longer than 6 foot lengths?
It comes in a 7 foot length as well as a 12 foot length.
Where can one purchase a used DB25 connector?
There are several websites and shops were you can purchase this type of connector. The main type of retailer would be an electrical store or another audio/visual retailer.
Can I use the Sabrent 6-Foot USB to DB25 Female Parallel Converter Adapter Printer Cable for any printer?
Any female USB cord will be great for a printer. Just double-check that it's an A to B cord.
What are the six functions of language?
The six functions of language are expressive (to express thoughts and feelings), directive (to give commands or requests), informative (to provide information), phatic (to establish social contact), aesthetic (to create beauty or evoke emotions), and metalinguistic (to discuss language itself).
A formula prewritten by excel is called?
Function
What is the parent function for the exponential function?
The parent function of the exponential function is ax
What function tests a specific condition in Excel?
The IF function is the main function to do it and you can also use other logical functions, like the AND function, the OR function or the NOT function.
