You can simply get all modems you got in the system by following:

svc=admin/modems&params={"callMode":"list",
			 "flags":<uint>}

[
	{
		"id": <long>,	/* modem id */
		"n": <text>,	/* name */
		"ph": <text>,	/* phone number */
		"ri": <uint>,	/* restart interval */
		"pr": <byte>,	/* priority */
		"pd": <text>,	/* preferred destinations */
		"f": <uint>,	/* modem flags */
		"e": <bool>.	/* state: 0 - off, 1 - on */
	},
	...
]

[
	{
		"id": <long>,	/* modem id */
		"n": <text>,	/* name */
		"ph": <text>,	/* phone number */
		"ri": <uint>,	/* restart interval */
		"pr": <byte>,	/* priority */
		"pd": <text>,	/* preferred destinations */
		"f": <uint>,	/* modem flags */
		"e": <bool>.	/* state: 0 - off, 1 - on */
		"cfg": 
			{
				"addon_cmds": <text>,		/* Additional initialization AT commands */
				"baudrate": <text>,		/* port speed */
				"data_only": <text>,		/* Use 8-bit encoding only */
				"factory": <text>,		/* modem type */
				"log_facility": <text>,		/* log file path */
				"phones_filter": <text>,	/* phones mask */
				"port": <text>,			/* serial port */
				"sms_retry_count": <text>,	/* SMS retry count */
				"smssc": <text>			/* SMS service center */
			},
		"un": [
			<long>,		/* unit id */
			...
		],
		"bp": [
			<long>,		/* billing plan id */
			...
		]
	},
	...
]