smb@research.att.com (10/07/88)
I'm interested in the wiring of the 50-pin jack for for 5-line keyset
telephones (2565HKM, if it matters). So far, I've learned that
there are 3 pairs allocated to each line, with 1 pair being tip and
ring, and the third pair being A and A1. I'm especially interested
in pins that are activated by the hold button, especially per-line
hold signals.
--Steve Bellovin
smb@ulysses.att.com
{att,ucbvax}!ulysses!smbdave@rutgers.edu (Dave Levenson) (10/10/88)
In article <telecom-v08i0154m08@vector.UUCP>, smb@research.att.com writes: > I'm interested in the wiring of the 50-pin jack for for 5-line keyset > telephones (2565HKM, if it matters). So far, I've learned that > there are 3 pairs allocated to each line, with 1 pair being tip and > ring, and the third pair being A and A1. I'm especially interested > in pins that are activated by the hold button, especially per-line > hold signals. > The first pair is tip and ring. The second is A and A1. The third is L and LG -- they light the line lamp. The hold command is sent by the phone to the KTU using the A and A1 pair. This pair is normally open. It is closed when the handset is offhook and the line button is selected. If you hang up (by placing the handset onhook or by releasing the line button by selecting another line) the tip and ring circuit opens before the A and A1 circuit. If you push the HOLD button, the A and A1 circuit opens before the Tip and Ring circuit. The KTU senses this timing and decides what the lamp state should be, and what to do about the hold relays. After using 3 pair per line (on the 2565 set) there is a pair for the ringer (common audible or CA pair) a pair for the buzzer (CA-1), several pair used for on-hook dialing when the set is associated with a type 3 or 4A speakerphone, a pair for the lamp under the HOLD key (seldom used), three pair for the exclusion key (the optional pull-up plunger that replaces one of the switchhook buttons) and a couple of pair for "locally engineered circuits". -- Dave Levenson Westmark, Inc. The Man in the Mooney Warren, NJ USA {rutgers | att}!westmark!dave
brian@umbc3.UMD.EDU (Brian Cuthie) (10/12/88)
In article <telecom-v08i0154m08@vector.UUCP> smb@research.att.com writes: >X-Administrivia-To: telecom-request@vector.uucp (USENET Telecom Moderator) > >I'm interested in the wiring of the 50-pin jack for for 5-line keyset >telephones (2565HKM, if it matters). So far, I've learned that >there are 3 pairs allocated to each line, with 1 pair being tip and >ring, and the third pair being A and A1. I'm especially interested >in pins that are activated by the hold button, especially per-line >hold signals. > > --Steve Bellovin > smb@ulysses.att.com > {att,ucbvax}!ulysses!smb Actually, in a 1A2 key system (that's what those five button phones are used for) the hold button works a little differently. When a phone is off hook, the KSU module detects loop current and the A1 lead activated by the button. So long as A1 is present with the loop current the line is considered to be active. However, if there is loop current but no A1 the line is placed on hold until A1 is present again or the loop current is dropped by the CO (usually indicating the the distant caller hung up). Thus, the hold button actually interrupts the A1 lead just prior to releasing the line key on the phone. This presents the condition described above and thus places the call on hold. This is also why answering machines and modems without A1 leads will leave a 1A2 system line on hold. Terminating a call normally requires that loop current be dropped along with A1. Cheers, brian