Compaq 1610 Reference Manual page 123

This apparatus has been approved for the following facilities:
Simple modem
Facsimile
Automatic call initiation
Detection of initial proceed indication
Automatic dialing
Tone detection of busy tone, dial tone, or number
unobtainable tone
Auto clear from the call origination end
Loop disconnect (pulse) dialing
Multifrequency (tone) dialing
Any other usage will invalidate the approval of the apparatus if,
as a result, it ceases to conform to the standards against which
approval was granted.
All apparatus connected to this modem and, thereby, connected
directly or indirectly to the British Telecom Public Switched
Telephone Network, must be approved apparatus as defined in
Section 16 of the British Telecommunications Act of 1981.
Although this equipment can use either loop disconnect or DTMF
signaling, only the performance of the DTMF signaling is subject
to regulatory requirements for correct operation. It is therefore
strongly recommended that the equipment be set to use DTMF
signaling for access to public or private emergency services.
DTMF signaling also provides faster call setup.
This device is intended for auto-answering of incoming calls.
Under normal conditions, callers will be accustomed to calls
being answered within 10 seconds, and a majority of callers will
abandon calls that are not answered within 45 seconds.
There are several options available for auto-answering operation.
The default setting is for two incoming rings. This is the
recommended setting for normal operation by most computer and
handheld PC users.