Modem AT command help - Page 1
Forum section: electronics / general

author: steve30
author_rank: Frequent Contributor
timestamp: June 11, 2016, 09:12:56 pm
content: I've been playing with modems this weekend.I have a USRobotics Courier model 3453C which I bought a couple of years ago. The command reference states that it should go off hook if it is issued with the command ATH1, and go on hook with ATH0. But neither of these commands seem to do anything. It will go off hook with the command ATA, but I'd like to be able to use ATH1 and ATH0.I tried another modem with these commands and it worked as expected so I'm sure its not just me that's going doolally. The Courier modem has commands, registers and DIP switches for practically everything, so I'm not sure if something might be set which is disabling the ATH commands, but I can't seem to find anything.Anyone got any ideas?Thankssteve30.

author: uncle_bob
author_rank: Unknown
timestamp: June 11, 2016, 09:50:33 pm
content: Quote from: steve30 on June 11, 2016, 09:12:56 pmHiWhat rev of the firmware does the modem have? Does it have a custom version? I'd update it to the current rev if there is any doubt.Bob

author: helius
author_rank: Super Contributor
timestamp: June 11, 2016, 10:00:31 pm
content: You may not hear that the modem is picking up if the speaker is disabled.

author: mettlerr
author_rank: Unknown
timestamp: June 11, 2016, 11:46:17 pm
content: Is the AT command set activated? DIP Switch 8 must be ON.Also try to sent an ATM1 first to turn the speaker on.

author: grantbob
author_rank: Unknown
timestamp: June 12, 2016, 12:41:19 am
content: Does the OH led on the front of the unit come on when you send ATH1 ? If not, I don't think it's getting your command.-grantbob

author: helius
author_rank: Super Contributor
timestamp: June 12, 2016, 01:54:26 am
content: I picked up one of these too from a skip, but without a power pack.Could you tell me what voltage it uses, center positive, etc? Thanks!

author: steve30
author_rank: Frequent Contributor
timestamp: June 12, 2016, 03:16:28 am
content: Quote from: helius on June 12, 2016, 01:54:26 amThe PSU which came with mine is 15V DC @ 0.8A, centre positive.The bottom of the modem itself says it will accept either 20V AC @ 0.75A, or 12 to 20V DC @ 0.8A.@Everyone else; Thanks for the replies. I will check the firmware versions, but as far as I can tell, it looks pretty standard. DIP switch 8 is set correctly, the speaker is enabled (you can here it pick up when issuing ATA, or when dialing with ATDT etc). The OH light doesn't come on when issuing ATH1.

author: mettlerr
author_rank: Unknown
timestamp: June 12, 2016, 07:47:38 am
content: Do you get any message back if you issue a ATH1 command?To enable messages:Enable message display ATQ0Display verbal messages ATV1Oh, and: In the terminal program or other program you are using to control the modem, do you send an init-AT-string with any configuration to the modem at start? Maybe something is turning off the standard behaviour?

author: grantbob
author_rank: Unknown
timestamp: June 12, 2016, 11:03:19 am
content: Quote from: steve30 on June 12, 2016, 03:16:28 amThat's odd. The only other thing I can think of is that on some of the modems the Line jack and the Phone jack are not interchangeable (not just wired in parallel) and when you send an ATH1 ,ATA, ATDT555 or whatever the Line jack is the one that off hook and the Phone jack is disconnected. I still think you'd hear a relay click and the OH led would come on.