E&M Signaling Format (E&M Only)

The E&M Signaling Format parameter is used to select one of four methods to signal (and sense) the on-hook/off-hook condition of an E&M telephone connection, as follows: DC, 2280 Tone, Pulsed DC, and Wink Start.

• DC -- The channel senses the active/idle condition of the remote end by the dc level on its M lead, and signals to the remote end its active/idle condition by a dc level on its E lead.
• 2280 Tone -- The channel senses the idle condition of the remote end by the presence of a 2280-Hz tone on its T-R pair, and holds a 2280-Hz tone on its T1-R1 pair to indicate its idle condition to the remote end. This option is applicable only to 4-wire connections.
• Pulsed DC -- A call connect request is made by sending a pulse of a medium duration on the transmit lead, and the call request is acknowledged by a return pulse of the same duration on the receive lead.
• Wink Start -- The Wink Start feature is designed to support voice switching between selected PBXs, such as the AT&T Legends. When selected, the user at the originating PBX seizes the M-lead and waits for a wink signal response from the local voice channel. Only then does the originating PBX forward the dialed digits to the destination voice channel. At the destination end, the voice channel seizes the E-lead and starts a regeneration delay timer (see Regeneration Delay). When the delay timer expires, the remaining digits are forwarded to the destination PBX.

Example:

As shown below, the user at the Los Angeles PBX attempts to reach station 56 at the Dallas PBX. To do that, the user goes off-line, waits for a dial tone from the PBX, then dials the number string 6123456.Trunk access code 6 causes the Los Angeles PBX to store digits 123456, seize the trunk M lead, and wait for a wink signal response from the Los Angeles voice channel on its E lead. Upon receipt of the wink signal response, the Los Angeles PBX forwards digits 123456 on the T/R lines to the Los Angeles Passport 4400 unit. Having made a determination that 1234 is not a local but a Dallas network extension, it forwards 1234 to the Dallas Passport 4400 unit.

Next, the Dallas voice channel goes off-hook by seizing the E lead, and starts a regeneration delay timer. When the regeneration delay time expires, the voice module forwards digits 56 in DTMF or pulse form, as configured, to the Dallas PBX. In turn, the Dallas PBX rings station 56. Connection is established when Dallas station 56 goes off-hook. It is assumed that the Dallas PBX will have responded with a wink signal on the M lead during the regeneration delay time.