The OpenLine product range offers low cost 4 port Computer Telephony (CT) cards.  The cards are specifically targeted for developers of PC based VOIP/Auto Attendant/Voicemail/ IVR applications.  The following table summarises the differences between the OpenLine cards:
 

Product	Bus	Caller ID Detection	Drivers	Approvals	Form Factor
OpenLine4	PCI	Yes	Linux, FreeBSD-4.4, Windows 98/2000/NT	US, Europe, Australia, New Zealand	half size PCI
OpenLine4i	ISA	No	Linux, FreeBSD, Windows NT/2000	Australia	full size ISA

Pricing

Prices are in US$ and exclude delivery and local taxes.
 

Number of Units	OpenLine4 Price Per Unit	OpenLine4i Price Per Unit
1-4	US$550	US$450
5-10	US$475	US$400
10+	Ask	Ask

Features

• Four terminating analogue (loop start) telephone ports. These ports are functionally and electrically equivalent to a telephone and are capable of terminating lines from an external exchange or PBX.
• Fixed point DSP that performs control, signal processing, and Host PC communications functions.
• Comprehensive API.
• Call Progress Analysis.
• DTMF detection and generation.
• User defined tone generation and detection.
• Voice compression modes: ADPCM at 32 kbit/s, 64 kbit/s A-law and mu-law PCM, 128kbit/s linear PCM.
• DSP echo cancellation - ideal for VOIP.
• Caller ID (OpenLine4 only).

For OpenLine4i technical specifications, see here.