Lucent Technologies 5 manual Issue

MERLIN LEGEND Communications System Release 5.0	Issue 1
System Manager’s Guide 555-650-118	June 1997

2About the System

Background Page 2-5

from the cradle (off-hook), current flows and signals the CO that the caller is requesting service.

Similarly, the CO signals the called party by sending current to his or her phone, causing it to ring. When the called party lifts the handset from its cradle, the current flows, indicating to the CO that the party has answered.

Bell realized that a caller needed a way to signal the other person to pick up the phone. After experiments with various bells and buzzers, in 1878 Bell’s assistant Watson developed a bell ringer operated by a hand crank.

When human operators handled switching, the caller used the telephone’s hand crank to ring the operator, and then told the operator the name of the person he or she wanted to reach. If the called party was available, the operator connected the two parties by using a cord that had plugs at each end. Each plug had parts called a tip and a ring that functioned as conductors to complete the electrical circuit.

The operator connected the two parties by plugging in one end of the cord into the caller’s connector (called a jack) on the switchboard, and the other end of the cord into the called party’s jack.

Once automatic switches were in place, telephone companies assigned numbers to telephone service subscribers, and a dialing mechanism was built into the telephone. The caller identified the called party to the switch by dialing the called party’s number.

Telephone users originally dialed numbers by using a mechanical device called a rotary dialer. A spring wound up when turned in one direction and, on its return to normal position, caused interruptions in the flow of current, thus creating dial pulses recognized by the switch. The subsequent development of the touch-tone dialer provided a further innovation: the creation of unique tones produced by simply pressing buttons on the dialpad.

Although there are still some rotary-dial telephones in use, most modern telephones have touch-tone dialing, which is faster and, with the advent of services available from touch-tone phones, more versatile.

The terms tip and ring, however, still describe any telephone equipment that involves only one line, for example, a single-line telephone (such as those in most homes), an answering machine, or a fax machine. These are referred to as tip/ring (T/R) devices.

You can use several different types of telephones with the MERLIN LEGEND Communications System, including single-line telephones, analog multiline telephones, and MLX digital telephones. The terms analog and digital refer to the type of signal the telephone produces:

■Analog Signal. A signal that represents a range of frequencies, that is, continuously variable physical qualities such as amplitude; for example, the human voice.