You can page through the phones on the side by side system if you follow what stsguy says above. You'll have to use DISA, program a button to dial the DISA answering number and then program a button with the remote access password then Feature 78 for a pause then enter *610 to page the phones only, *630 to page overhead and the phones or simply *62 to just page the overhead speakers.
I tried this out in my Test lab for you....
First set up a DISA trunk say on an unused analog CO or PRI line, you can't use SIP lines. DISA seems to work best with analog lines.
Second, Program an Autodial button with the Remote access password, Feature 78 and then *630 to page the system.
example say 311 is the password:
-Press Feature *1 to program the autodial button
-When the phone says enter digits, enter: 311F78*630
Test the function by dialing the Trunk line, wait for DISA to pick up after the second ring (you'll hear a stuttered dial tone) and THEN press the autodial button, you'll hear a dial tone again and then silence....when you hear the silence you can speak. Press RLS or hang up to end the page.
In order to convey to the user:
Set up an Autodial button on their phone that dials the DISA trunk and label it DIAL PAGE
Then set up a second autodial button on it that automatically enter the COS password and *630. Maybe label it SAY PAGE.
Make sure the user knows to wait for the phone to stop ringing and then hear dial tone.
You are ready to make and receive pages.
Note though, on the page receiving system, you aren't going to get a nice clean silent release noise if you are using analog trunks to do this, you are more than likely going to get a POP or Click when the page is completed.
Also note, I tried saving the whole sequence in one button and it didn't work....too many digits doing too many things seems to confuse the system, so thats why I split this up into 2 buttons.