E and M Signaling - Address Signaling

Address Signaling

The mechanisms described so far only allow circuit seizure - on-hook and off-hook - to be signaled. In order to allow dialing over the interface, "start" signaling mechanisms are defined. This allows the other end to know when to send the dialed digits, which are transmitted by pulse (loop disconnect) or multi-frequency tones. E&M defines three methods of "start" signaling:

• Wink Start - when the originator goes off hook, the other end transmits a short (140-290ms) off-hook signal and returns to on-hook. The originator detects the wink and then sends the dialed digits. The other end goes permanently off-hook (seized) when the call is answered.
• Delay Start - the originator goes off hook, waits a pre-defined delay, and then checks for on-hook from the other end before sending the digits.
• Immediate Start - The originator goes off hook, waits 150ms and then sends the dialed digits.