Stickdog Telecom Group

Listen for dial tone and push the code for the special ringing pattern you wish to use: * 51 (dial 1-1-5-1 for rotary phones) for two short rings or * 52 (1-1-5-2 for rotary phones) for one short ring, one long ring and another short ring.
Listen for the confirmation tone (two short tones followed by a dial tone) and hang up within 15 seconds.
All the extensions of that telephone number will ring with the appropriate special ringing pattern. (Note: All telephones that share the same telephone number are called extensions.)
Ringing will stop when any extension is answered, including the extension from which the call was placed.
When any extension is answered, the Intercom call is activated.
When all extensions hang up, the Intercom call is deactivated.

To transfer a non-Intercom call to another extension, press the switchhook briefly, putting the party on hold. Listen for three short tones and then a dial tone.
Press the intercom code (* 51 or dial 1-1-5-1, * 52 or dial 1-1-5-2) for the special ringing pattern of the person or extension the caller is trying to reach.
Listen for the confirmation tone (two short tones followed by a dial tone), then hang up within 15 seconds.
All extensions will ring until any extension is answered. The extension that answered will then be connected with the party on hold.

To place any call on hold (either incoming or outgoing), press the switchhook briefly, placing the party on temporary hold.
Listen for the special dial tone. Press * 53 (dial 1-1-5-3 for rotary phones) to activate Call Hold.
Listen for the confirmation tone and hang up within 15 seconds.
The call remains on hold until any extension is answered or the party on hold hangs up.

To add a third party to your call, press the switchhook briefly, putting your first party on hold.
Listen for three short tones and then a dial tone. Dial the telephone number for the person you want to add to the conversation. When that person answers, bring the first party into the conversation by briefly pressing the switchhook once.
If the second line is busy or there is no answer, you can return to the original party by pressing the switchhook twice.