Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!cbatt!UCBVAX.BERKELEY.EDU!SPGDCM%cmsa.Berkeley.EDU From: SPGDCM%cmsa.Berkeley.EDU@UCBVAX.BERKELEY.EDU.UUCP Newsgroups: mod.telecom Subject: Hold Circuit Message-ID: <8612110705.AA22744@ucbvax.Berkeley.EDU> Date: Fri, 5-Dec-86 01:45:44 EST Article-I.D.: ucbvax.8612110705.AA22744 Posted: Fri Dec 5 01:45:44 1986 Date-Received: Sun, 14-Dec-86 10:48:14 EST Sender: daemon@ucbvax.BERKELEY.EDU Organization: The ARPA Internet Lines: 33 Approved: telecom@xx.lcs.mit.edu Years ago I saw (I think in an electronics hobbyist magazine) a very simple circuit which one could add to any phone to gain an illuminated "hold" function. It worked on regular twisted-pair phones; it worked only on the phone you wired this way. As best I remember it, it was something like a zener diode, a resistor, a temporary-connect push-button, and an led; maybe a neon light instead but I think not. The concept was that once your button made the connection, the zener diode effectively shorted the line enough to hold onto the circuit (one would need to draw the voltage down to say 10v). Then if any other extension went off-hook, it would draw the line down to 5v. which somehow dropped the zener out and it let go, as a good hold should. The LED got activated properly somehow so that it glowed on the held instrument until an intercept or that instrument went off-hook and dropped hold. Now I am really sad I lost the diagram, because I want to add hold to all my phones. Costs too much to upgrade them all when I could add this instead for say $2-4 each. Anybody know the circuit? Especially useful would be the exact component values, preferably within the set widely available such as Radio Shack, or if necessary with a source of supply if the values are rare. P.S.: unfortunately many commonly-sold phones still don't offer hold, but even worse, many offer what I would like to see called "false-hold": you can flip a dumb toggle or slide switch on the phone to "hold" the line, but must shut that particular switch off to unhold; really a mute toggle, not a hold. Some store's ads (such as San Francisco Macy's) call this hold, and you waste a visit to the store. Some mail-order houses have had to resort to calling the correct feature "true-hold". Hmmm... as if you had to see words like "real food" or "true-movies" in ads or else get cheated... Thanks, Doug